HK40070148B - Arginase inhibitors and methods of use thereof - Google Patents

Description

Arginase inhibitors and their usage

Background Technology

Arginase is a manganese metalloenzyme that catalyzes the conversion of L-arginine to urea and L-ornithine. Two isoforms exist: arginase 1 is a cytoplasmic enzyme primarily found in hepatocytes, where it plays a crucial role in the removal of ammonia through urea synthesis; while arginase 2 is a mitochondrial enzyme highly expressed in the kidneys, involved in the production of ornithine, a precursor to proline and polyamines important for cell proliferation and collagen production, respectively.

Although L-arginine is not an essential amino acid, as it can be obtained through protein conversion in healthy adults, increased expression and secretion of arginase under various physiological and pathological conditions (e.g., pregnancy, autoimmune diseases, cancer) lead to decreased L-arginine levels. Immune cells, in particular, are sensitive to decreased L-arginine levels. When faced with a low-L-arginine microenvironment, T cells reduce their proliferation rate and decrease the expression of CD3ζ chain, IFNγ, and lyases, resulting in impaired T cell responsiveness. Dendritic cells respond to low-L-arginine conditions by reducing their antigen-presenting capacity, and natural killer cells reduce the proliferation and expression of lyases.

Tumors employ a variety of immunosuppressive mechanisms to evade the immune system. One of these is by increasing the level of circulating arginase, increasing arginase expression and secretion in tumor cells, and recruiting myeloid-derived suppressor cells that express and secrete arginase to reduce L-arginine levels. These mechanisms together lead to reduced L-arginine in the tumor microenvironment and produce an immunosuppressive phenotype. Pharmacological inhibition of arginase activity has been shown to reverse low L-arginine-induced immunosuppression in animal models. Therefore, potent and selective arginase inhibitors are needed, either as single agents or in combination with therapies that reverse other immunosuppressive mechanisms, to reverse immunosuppression and reactivate the patient's anti-cancer immunity.

Summary of the Invention

In some embodiments, a compound having formula (I) or a pharmaceutically acceptable salt thereof is disclosed:

in

^R1 is selected from hydrogen, _-CH3 , and -(C=O)CH( ^R1a ) _NH2 ;

R ^1a is a _C1 - _C4 alkyl group;

Y is -( _CH₂ ) _n- or -(C=O)-;

n is an integer chosen from 1 and 2;

^R2 is selected from hydrogen, _-CH3 , and -(C=X) ^R4 , and ^R3 is hydrogen or _-CH3 ; or

^R2 and ^R3 are linked together with the nitrogen to which they are attached to form a nitrogen-containing 6-membered heterocycle;

X is NH or O;

^R4 is _-CH3 or -[CH( ^R4a )] _{mNH2 ;}

m is an integer selected from 0 or 1; and

^R4a is hydrogen or _C1 - _C4 alkyl.

In some embodiments, a compound having formula (II) or a pharmaceutically acceptable salt thereof is disclosed:

in

R ¹¹ is selected from hydrogen, -CH ₃ , and the * indicating (S) stereochemistry therein;

^Y1 is -( _CH2 ) _p- or -(C=O)-;

p is an integer selected from 1 and 2;

R ^11a is a _C1 - _C4 alkyl group;

^R12 is selected from hydrogen, _-CH3 , and -(C= ^X1 ) ^R14 , and ^R13 is hydrogen or _-CH3 ; or

^R12 and ^R13 are linked together with the nitrogen to which they are attached to form a nitrogen-containing 6-membered heterocycle;

X ¹ is NH or O;

R ¹⁴ is -CH ₃ or where * indicates (S) stereochemistry;

R ^14a is a _C1 - _C4 alkyl group; and

q is an integer selected from 0 and 1.

In some embodiments, compounds having formula (III) or pharmaceutically acceptable salts thereof are disclosed:

in

R ²² is hydrogen or where * indicates (S) stereochemistry; and

R ^24a is a _C1 - _C4 alkyl group.

In some embodiments, a compound having formula (IV) or a pharmaceutically acceptable salt thereof is disclosed:

in

R ¹¹ is where * indicates (S) stereochemistry; and R ^11a is _C1 - _C4 alkyl.

In some embodiments, the compounds in Table 1 or their pharmaceutically acceptable salts are disclosed.

In some embodiments, a pharmaceutical composition is disclosed comprising a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

In some embodiments, methods for treating cancer are disclosed, including administering a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof.

In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1, or pharmaceutically acceptable salts thereof, are disclosed for the treatment of cancer.

In some embodiments, the use of compounds having (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof in the manufacture of a medicament for use in the treatment of cancer is disclosed.

In some embodiments, pharmaceutical compositions are disclosed comprising compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof, for use in the treatment of cancer.

In some embodiments, methods for treating inflammatory respiratory diseases are disclosed, including the administration of compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof.

In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof are disclosed for the treatment of inflammatory respiratory diseases.

In some embodiments, the use of chemicals having (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof in the manufacture of a medicament for use in the treatment of inflammatory respiratory diseases is disclosed.

In some embodiments, pharmaceutical compositions are disclosed comprising compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof, for use in the treatment of inflammatory respiratory diseases.

In some embodiments, the aforementioned inflammatory respiratory disease is chronic obstructive pulmonary disease (COPD) or asthma.

Detailed Implementation

In some embodiments, a compound having formula (I) or a pharmaceutically acceptable salt thereof is disclosed:

in

^R1 is selected from hydrogen, _-CH3 , and -(C=O)CH( ^R1a ) _NH2 ;

R ^1a is a _C1 - _C4 alkyl group;

Y is -( _CH₂ ) _n- or -(C=O)-;

n is an integer chosen from 1 and 2;

^R2 is selected from hydrogen, _-CH3 , and -(C=X) ^R4 , and ^R3 is hydrogen or _-CH3 ; or

^R2 and ^R3 are linked together with the nitrogen to which they are attached to form a nitrogen-containing 6-membered heterocycle;

X is NH or O;

^R4 is _-CH3 or -[CH( ^R4a )] _{mNH2 ;}

m is an integer selected from 0 or 1; and

^R4a is a _C1 - _C4 alkyl group.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, and ^R2 and ^R3 are connected together with the nitrogen to which they are attached to form a nitrogen-containing six-membered heterocycle. In some embodiments, the nitrogen-containing six-membered heterocycle is a morpholino ring. In some embodiments, the nitrogen-containing six-membered heterocycle is a piperidinyl ring.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is _-CH3 , and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is _-CH3 , and ^R3 is _-CH3 .

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is NH, ^R4 is [CH( ^R4a )] _mNH2 , and m is ₀ .

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is [CH( ^R4a )] _mNH2 , and m is ₀ .

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C3 alkyl group (e.g., isopropyl).

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4m , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _mNH2 , m is 1, and ^R4a is _{a C2} alkyl group (e.g., ethyl).

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C1 alkyl group (e.g., methyl).

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, and ^R4 is _-CH3 .

In some embodiments, in a compound having formula (I), ^R1 is _-CH3 , Y is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is -(C=O)CH( ^R1a ) _NH2 , ^R1a is a _C3 alkyl (e.g., isopropyl), R is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is -(C=O)CH( ^R1a ) _NH2 , ^R1a is a _C1 alkyl group (e.g., methyl), R is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 2, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -(C=O), ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -(C=O), ^R2 is _-CH3 , and ^R3 is hydrogen.

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _mNH2 , m is 1, _and ^R4a is a _C4 alkyl (e.g., isobutyl).

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _mNH2 , m is 1, and ^R4a is _{a C4} alkyl (e.g., tert-butyl).

In some embodiments, in a compound having formula (I), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is hydrogen.

In some embodiments, a compound having formula (I) or a pharmaceutically acceptable salt thereof is a compound having formula (Ia):

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, and ^R2 and ^R3 are connected together with the nitrogen to which they are attached to form a nitrogen-containing six-membered heterocycle. In some embodiments, the nitrogen-containing six-membered heterocycle is a morpholino ring. In some embodiments, the nitrogen-containing six-membered heterocycle is a piperidinyl ring.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is _-CH3 , and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is _-CH3 , and ^R3 is _-CH3 .

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is NH, ^R4 is [CH( ^R4a )] _mNH2 , and m is ₀ .

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is [CH( ^R4a )] _mNH2 , and m is ₀ .

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C3 alkyl group (e.g., isopropyl).

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4m , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _mNH2 , m is 1, and ^R4a is _{a C2} alkyl group (e.g., ethyl).

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C1 alkyl group (e.g., methyl).

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, and ^R4 is _-CH3 .

In some embodiments, in a compound having formula (Ia), ^R1 is _-CH3 , Y is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is -(C=O)CH( ^R1a ) _NH2 , ^R1a is a _C3 alkyl (e.g., isopropyl), R is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is -(C=O)CH( ^R1a ) _NH2 , ^R1a is a _C1 alkyl group (e.g., methyl), R is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 2, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -(C=O), and ^R2 and ^R3 are hydrogen.

In some embodiments, in a compound having formula (Ia), ^R1 is hydrogen, Y is -(C=O), ^R2 is _-CH3 , and ^R3 is hydrogen.

In some embodiments, a compound having formula (I) or a pharmaceutically acceptable salt thereof is a compound having formula (Ib):

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is hydrogen, and ^R3 is hydrogen.

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C3 alkyl group (e.g., isopropyl).

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C1 alkyl group (e.g., methyl).

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _mNH2 , m is 1, and ^R4a is _{a C2} alkyl (e.g., ethyl).

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is a _C4 alkyl group (e.g., isobutyl or tert-butyl).

In some embodiments, in a compound having formula (Ib), ^R1 is hydrogen, Y is -( _CH2 ) _n- , n is 1, ^R2 is -(C=X) ^R4 , ^R3 is hydrogen, X is O, ^R4 is -[CH( ^R4a )] _{mNH2 ,} m is 1, and ^R4a is hydrogen.

In some embodiments, a compound having formula (II) or a pharmaceutically acceptable salt thereof is disclosed:

in

R ¹¹ is selected from hydrogen, -CH ₃ and the * indicating (S) stereochemistry therein;

^Y1 is -( _CH2 ) _p- or -(C=O);

p is an integer selected from 1 and 2;

R ^11a is a _C1 - _C4 alkyl group;

^R12 is selected from hydrogen, _-CH3 , and -(C= ^X1 ) ^R14 , and ^R13 is hydrogen or _-CH3 ; or

^R12 and ^R13 are linked together with the nitrogen to which they are attached to form a 6-membered heterocycle;

X ¹ is NH or O;

R ¹⁴ is -CH ₃ or where * indicates (S) stereochemistry;

R ^14a is a _C1 - _C4 alkyl group; and

q is an integer selected from 0 and 1.

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is hydrogen, and ^R13 is hydrogen.

In some embodiments, in the compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, and ^R12 and ^R13 are connected together with the nitrogen to which they are attached to form a 6-membered nitrogen-containing heterocycle. In some embodiments, the nitrogen-containing six-membered heterocycle is a morpholinoyl ring. In some embodiments, the nitrogen-containing six-membered heterocycle is a piperidinyl ring.

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is _-CH3 , and ^R13 is hydrogen.

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is _-CH3 , and ^R13 is _-CH3 .

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is NH, ^R14 is and q is 0.

In some embodiments, in the compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is O, ^R14 is and q is 0.

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is O, ^R14 is q is 1, and ^R14a is _C3 alkyl (e.g., isopropyl).

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is O, ^R14 is q is 1, and ^R14a is _C2 alkyl (e.g., ethyl).

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is O, ^R14 is q is 1, and ^R14a is _C1 alkyl (e.g., methyl).

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is -(C= ^X1 ) ^R14 , ^R13 is hydrogen, ^X1 is O, and ^R14 is _-CH3 .

In some embodiments, in a compound having formula (II), ^R11 is _-CH3 , ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is hydrogen, and ^R13 is hydrogen.

In some embodiments, in a compound having formula (II), ^R11 is ^R11a is a _C3 alkyl group (e.g., isopropyl), ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is hydrogen, and ^R13 is hydrogen.

In some embodiments, in a compound having formula (II), ^R11 is ^R11a is a _C1 alkyl group (e.g., methyl), ^Y1 is -( _CH2 ) _p- , p is 1, ^R12 is hydrogen, and ^R13 is hydrogen.

In some embodiments, in a compound having formula (II), ^R11 is hydrogen, ^Y1 is -( _CH2 ) _p- , p is 2, ^R12 is hydrogen, and ^R13 is hydrogen.

In some embodiments, in a compound having formula (II), R ¹¹ is hydrogen, Y ¹ is -(C=O), R ¹² is hydrogen, and R ¹³ is hydrogen.

In some embodiments, in a compound having formula (II), R ¹¹ is hydrogen, Y ¹ is -(C=O), R ¹² is -CH ₃ , and R ¹³ is hydrogen.

In some embodiments, compounds having formula (III) or pharmaceutically acceptable salts thereof are disclosed:

in

R ²² is hydrogen or where * indicates (S) stereochemistry; and

R ^24a is a _C1 - _C4 alkyl group.

In some embodiments, in compounds having formula (III), R ²² is hydrogen.

In some embodiments, in compounds having formula (III), ^R22 is and ^R24a is a _C3 alkyl group (e.g., isopropyl).

In some embodiments, in compounds having formula (III), ^R22 is and ^R24a is a _C1 alkyl group (e.g., methyl).

In some embodiments, in compounds having formula (III), ^R22 is and ^R24a is a _C2 alkyl group (e.g., ethyl).

In some embodiments, in compounds having formula (III), ^R22 is and ^R24a is a _C4 alkyl group (e.g., isobutyl or tert-butyl).

In some embodiments, a compound having formula (IV) or a pharmaceutically acceptable salt thereof is disclosed:

in

R ¹¹ is where * indicates (S) stereochemistry; and R ^11a is _C1 - _C4 alkyl.

In some embodiments, the compounds in Table 1 or their pharmaceutically acceptable salts are disclosed:

Table 1

The term " _C1 - _C4 alkyl" includes acyclic saturated alkyl moieties having 1 to 4 carbon atoms. Examples of _C1 - _C4 alkyl moieties include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl.

The term "nitrogen-containing six-membered heterocycle" includes a saturated cycloalkyl moiety having at least one carbon replaced by nitrogen. Examples of nitrogen-containing six-membered heterocycles include piperidine, piperazine, morpholine, thiomorpholine, and hexahydro-1,3,5-triazine.

The term "pharmaceutically acceptable salt" includes compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and those listed in Table 1 that retain the bioavailability and properties of such compounds and are typically not biologically or otherwise undesirable acid or base addition salts. In many cases, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and those listed in Table 1 are capable of forming acid salts and/or base salts due to the presence of a basic and/or carboxyl group or similar groups.

Pharmaceutically acceptable acid addition salts can be formed using inorganic and organic acids, such as acetates, aspartates, benzoates, benzenesulfonates, bromides/hydrobromates, bicarbonates/carbonates, bisulfates/sulfates, camphorsulfonates, chlorides/hydrochlorides, chlortheophyllonates, citrates, ethanedisulfonates, fumarates, glucohepanoates, glucuronates, hippurates, and hydroiodates. Iodides, hydroxyethyl sulfonates, lactates, lactobionates, lauryl sulfate, malates, maleates, malonic acids, mandelicates, methanesulfonates, methyl sulfates, naphthates, naphthalenesulfonates, nicotinates, nitrates, stearates, oleates, oxalates, palmitates, palmoate, phosphates/hydrogen phosphates/dihydrogen phosphates, polygalacturonic acids, propionates, stearates, succinates, basic salicylates, sulfates/hydrogen sulfates, tartrates, toluenesulfonates, and trifluoroacetates. Inorganic acids from which salts can be derived include, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, and phosphoric acid. Organic acids from which salts can be derived include, for example, acetic acid, propionic acid, glycolic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, toluenesulfonic acid, trifluoroacetic acid, and sulfosalicylic acid.

Pharmaceutically acceptable base addition salts can be formed from inorganic and organic bases. Inorganic bases from which salts can be derived include, for example, ammonia, as well as salts of ammonium and metals from columns I through XII of the periodic table. In some embodiments, salts are derived from sodium, potassium, ammonium, calcium, magnesium, iron, silver, zinc, and copper; particularly suitable salts include ammonium, potassium, sodium, calcium, and magnesium salts. Organic bases from which salts can be derived include, for example, primary, secondary, and tertiary amines; substituted amines (including naturally occurring substituted amines); cyclic amines; basic ion exchange resins, etc. Some organic amines include isopropylamine, benzathine, cholinate, diethanolamine, diethylamine, lysine, meglumine, piperazine, and tromethamine.

Pharmaceutically acceptable salts of compounds having formulas (I), (Ia), (Ib), (II), (III), and (IV) and those listed in Table 1 can be synthesized from the basic or acidic fractions using conventional chemical methods. Typically, such salts are prepared by reacting the free acidic form of these compounds with a stoichiometric amount of a suitable base (such as hydroxides, carbonates, bicarbonates, etc. of ^Na⁺ , ^Ca²⁺ , ^Mg²⁺ , or ^K⁺ ), or by reacting the free basic form of these compounds with a stoichiometric amount of a suitable acid. Typically, such reactions are carried out in water, in an organic solvent, or in a mixture of both. Generally, where feasible, the use of non-aqueous media such as ether, ethyl acetate, ethanol, isopropanol, or acetonitrile is preferable. Other suitable lists of salts can be found, for example, in: “Remington’s Pharmaceutical Sciences,” 20th edition, Mack Publishing Company, Easton, Pa. (1985); Berge et al., “J. Pharm. Sci.”, 1977, 66, 1–19; and Stahl and Wermuth, “Handbook of Pharmaceutical Salts: Properties, Selection, and Use” (Wiley-VCH, Weinheim, Germany, 2002).

Any formulas given herein are also intended to represent the unlabeled and isotopically labeled forms of compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and the compounds in Table 1, or their pharmaceutically acceptable salts. Isotopically labeled compounds have the structures described by the formulas given herein, except that one or more atoms are replaced by atoms of the same element but with different mass numbers. Examples of isotopes that can be incorporated into compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and the compounds in Table 1, or their pharmaceutically acceptable salts, include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, fluorine, chlorine, and iodine, such as ^2H , ^3H , ^11C , ^13C , ^14C , ^15N , ^35S , ^36Cl , and ^125I . Isotopically labeled compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and the compounds in Table 1 can generally be prepared by conventional techniques known to those skilled in the art or by methods similar to those described in the accompanying examples, using appropriate isotopically labeled reagents instead of previously used unlabeled reagents.

Compounds having formulas (I), (Ia), (Ib), (II), (III), and (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, may have different isomeric forms. The terms "optical isomer," "stereoisomer," or "diastereomer" refer to any of the various stereoisomeric configurations that may exist for a given compound having formulas (I), (Ia), (Ib), (II), (III), and (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof. It should be understood that substituents may be attached to the chiral center of a carbon atom; therefore, the disclosed compounds include enantiomers, diastereomers, and racemates. The term "enantiomer" includes paired stereoisomers that are non-overlapping mirror images of each other. A 1:1 mixture of a pair of enantiomers is a racemic mixture. Where appropriate, this term is used to refer to racemic mixtures. The term "diastereomer" or "diastereomer" includes stereoisomers having at least two asymmetric atoms that are not mirror images of each other. Absolute stereochemistry is specified according to the Cahn-Ingold-Prelog R-S system. When a compound is a pure enantiomer, the stereochemistry at each chiral center can be specified by R or S. Resolved compounds with unknown absolute configurations can be designated as (+) or (-) depending on the direction (right-handed or left-handed) of the plane-polarized light rotated at the sodium D-line wavelength. Certain compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and the compounds in Table 1, or their pharmaceutically acceptable salts, contain one or more asymmetric centers or axes and thus can produce enantiomers, diastereomers, or other stereoisomers, defined as (R)- or (S)- for absolute stereochemistry. This disclosure is intended to include all such possible isomers, including racemic mixtures, optically pure forms, and intermediate mixtures. Optically active (R)- and (S)- isomers can be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques well known in the art such as chiral HPLC.

This article also discloses intermediates 1 to 56 and their salts in the examples.

Pharmaceutical Composition

In some embodiments, a pharmaceutical composition is disclosed comprising a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

The term "pharmaceutically acceptable carrier" includes compounds, materials, compositions, and/or dosage forms that, as determined by a person skilled in the art, are suitable for use in human and animal tissues without excessive toxicity, irritation, allergic reactions, or other problems or complications, within the bounds of reasonable medical judgment.

The disclosed compositions may be in the form suitable for oral use (e.g., as tablets, lozenges, hard capsules or soft capsules, aqueous or oily suspensions, emulsions, dispersible powders or granules, syrups or elixirs), in the form suitable for topical use (e.g., as creams, ointments, gels or aqueous or oily solutions or suspensions), in the form suitable for inhalation (e.g., as fine powders or liquid aerosols), in the form suitable for inhalation (e.g., as fine powders), or in the form suitable for parenteral administration (e.g., as sterile aqueous or oily solutions for intravenous, subcutaneous, intramuscular or intramuscular administration or as suppositories for rectal administration).

The amount of active ingredient combined with one or more pharmaceutically acceptable carriers to produce a single dosage form will necessarily vary depending on the host being treated and the specific route of administration. Further information on routes of administration and dosage regimens can be found in Comprehensive Medicinal Chemistry, Volume 5, Chapter 25.3 (Editorial Board Chair Corwin Hansch), Pergamon Press, 1990.

Therapeutic practicality

The compounds of this invention can be used as arginase inhibitors in therapy.

In one aspect, methods for treating cancer in subjects in need are disclosed, including administering to the subject an effective amount of a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof.

In one aspect, methods for treating respiratory inflammatory diseases in subjects in need are disclosed, comprising administering to the subject an effective amount of a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof.

In one aspect, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1, or pharmaceutically acceptable salts thereof, are disclosed for use in the treatment of cancer.

In one aspect, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1, or pharmaceutically acceptable salts thereof, are disclosed for use in the treatment of inflammatory respiratory diseases.

In one aspect, the use of compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds or pharmaceutically acceptable salts of Table 1 in the manufacture of medicaments for the treatment of cancer is disclosed.

In one aspect, the use of compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds or pharmaceutically acceptable salts of Table 1 in the manufacture of medicaments for treating inflammatory diseases of the respiratory tract is disclosed.

In one aspect, pharmaceutical compositions are disclosed comprising compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof, for use in the treatment of cancer.

In one aspect, pharmaceutical compositions are disclosed comprising compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof, for use in the treatment of inflammatory respiratory diseases.

The term "cancer" includes, for example, renal cell carcinoma, head and neck squamous cell carcinoma, lung cancer (e.g., small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), mesothelioma), pancreatic cancer, colorectal cancer, breast cancer, acute myeloid leukemia (AML), prostate cancer, gastric cancer, bladder cancer, melanoma, kidney cancer, and ovarian cancer. In some embodiments, the cancer has metastasized. In some embodiments, the cancer is associated with the regulation of arginase 1 and/or arginase 2.

In some embodiments, cancer is associated with increased plasma arginase 1 levels. In some embodiments, cancer is associated with decreased plasma arginine levels. In some embodiments, cancer is associated with both increased plasma arginase 1 levels and decreased plasma arginine levels. In some embodiments, cancers associated with increased plasma arginase 1 levels and/or decreased plasma arginine levels include renal cell carcinoma, head and neck squamous cell carcinoma, lung cancer (e.g., small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), mesothelioma), pancreatic cancer, colorectal cancer, and breast cancer.

In some embodiments, cancers secrete arginase 2, such as acute myeloid leukemia and prostate cancer.

In some embodiments, cancer is associated with arginase 1-positive tumor-infiltrating immune cells, such as lung cancer (small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), gastric cancer, bladder cancer, colorectal cancer, melanoma, head and neck squamous cell carcinoma, breast cancer, prostate cancer, ovarian cancer, pancreatic cancer, and kidney cancer).

The term "inflammatory respiratory disease" refers to an inflammatory condition or disorder affecting the airways, pulmonary vascular system, pulmonary interstitium, or a combination thereof. These may be isolated to the lungs or involve multiple organs. In one embodiment, an inflammatory respiratory disease is inflammatory lung disease. In another embodiment, inflammatory lung disease is non-infectious. In some embodiments, inflammatory respiratory diseases are associated with the regulation of arginase 1 and/or arginase 2.

In some embodiments, the inflammatory respiratory disease is asthma, chronic obstructive pulmonary disease (COPD), chemically induced pulmonary fibrosis, idiopathic pulmonary fibrosis, cystic fibrosis, or a combination thereof. In some embodiments, the inflammatory respiratory disease is chronic obstructive pulmonary disease (COPD) or asthma.

In one aspect, methods for inhibiting arginase in subjects in need are disclosed, comprising administering to the subject an effective amount of a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1 or a pharmaceutically acceptable salt thereof.

In one aspect, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, are disclosed for use in inhibiting arginase.

In one aspect, the use of compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof in the manufacture of a medicament for inhibiting arginase is disclosed.

In one aspect, pharmaceutical compositions are disclosed comprising compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) or compounds in Table 1 or pharmaceutically acceptable salts thereof, for use in inhibiting arginase.

The term "arginase" includes manganese-containing enzymes belonging to the urea hydrolase family that catalyze the fifth and final step of the urea cycle, converting L-arginine to L-ornithine and urea. The term "arginase" includes two isoenzymes of this enzyme, such as arginase 1 and arginase 2. Arginase 1 functions in the urea cycle and is primarily located in the cytoplasm of the liver, while arginase 2 is located in the mitochondria of several tissues in the body and is involved in the regulation of arginine/ornithine concentrations in cells. In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), and (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, are selective for arginase 1. In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), and (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, are selective for arginase 2. In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, inhibit both arginase 1 and arginase 2.

The term "effective amount" includes the amount of a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1, or a pharmaceutically acceptable salt thereof, that will elicit, for example, a biological or medical response in a subject, such response as: reducing or inhibiting the activity of arginase or cancer-related enzymes or proteins; improving cancer symptoms; or slowing or delaying cancer progression. In some embodiments, the term "effective amount" includes, when administered to a subject, the amount of a compound having formula (I), (Ia), (Ib), (II), (III), (IV) or a compound in Table 1, or a pharmaceutically acceptable salt thereof, that is effective in at least partially reducing, inhibiting, and/or improving cancer or inhibiting arginase, and/or reducing or inhibiting tumor growth or cancer cell proliferation in the subject.

The term "subject" includes warm-blooded mammals such as primates, dogs, cats, rabbits, rats, and mice. In some embodiments, the subject is a primate, such as a human. In some embodiments, the subject has cancer. In some embodiments, the subject requires treatment (e.g., the subject would benefit biologically or medically from treatment). In some embodiments, the subject has increased plasma arginase 1 levels. In some embodiments, the subject has decreased arginine levels. In some embodiments, the patient has increased plasma arginase 1 levels and decreased arginine levels. In some embodiments, the subject has a cancer that secretes arginase 2 (e.g., acute myeloid leukemia or prostate cancer). In some embodiments, the subject has arginase 1-positive tumor-infiltrating immune cells.

The term "inhibit, inhibition, or inhibiting" includes a reduction in the baseline activity of a biological activity or process. In some embodiments, compounds having formulas (I), (Ia), (Ib), (II), (III), (IV) and compounds in Table 1, or pharmaceutically acceptable salts thereof, inhibit arginase.

The term "treatment" includes reducing or inhibiting the activity of enzymes or proteins associated with arginase or in a subject; improving one or more symptoms of cancer; or slowing or delaying the progression of cancer in a subject. The term "treatment" also includes reducing or inhibiting the growth of tumors or the proliferation of cancerous cells in a subject.

Example

Several aspects of this disclosure can be further defined by reference to the following non-limiting examples, which describe in detail the preparation of certain compounds and intermediates of this disclosure and methods for using the compounds disclosed. It will be apparent to those skilled in the art that many modifications can be made to the materials and methods without departing from the scope of this disclosure.

Unless otherwise stated:

(i) Unless otherwise stated, all synthesis shall be carried out at ambient temperature (i.e., in the range of 17°C to 25°C) and in an atmosphere of an inert gas such as nitrogen;

(ii) Evaporation is carried out in a vacuum by rotary evaporation or using a Genevac facility or Biotage v10 evaporator, and a processing procedure is performed after the residual solids are removed by filtration;

(iii) Rapid chromatographic purification was performed on automated Teledyne IscoRf or Teledyne Isco using pre-filled RediSep Rf Gold ^™ silica columns (20-40 μm, spherical particles), GraceResolv ^™ columns (silica), or Silicycle columns (40-63 μm).

(iv) Preparative chromatography was performed on a Gilson preparative HPLC instrument equipped with UV acquisition; alternatively, preparative chromatography was performed on a Waters automated purification HPLC-MS instrument equipped with MS and UV-triggered acquisition.

(v) Chiral preparative chromatography was performed on a Gilson instrument equipped with UV acquisition (233 injector/fraction collector, 333 and 334 pumps, 155 UV detector) or a Varian Prep Star instrument (two SD1 pumps, 325 UV detector, 701 fraction collector), with the pumps running with the Gilson 305 injection; alternatively, chiral preparative chromatography was performed on a Waters Prep100 SFC-MS instrument equipped with MS and UV-triggered acquisition or a Thar MultiGram III SFC instrument equipped with UV acquisition.

(vi) The yield (if it exists) does not have to be the maximum achievable value;

(vii) Generally, the structure of the final product having Formula I is confirmed by nuclear magnetic resonance (NMR) spectroscopy; NMR chemical shift values are measured at the delta level [proton magnetic resonance spectra are determined using a Bruker Avance 500 (500 MHz), Bruker Avance 400 (400 MHz), Bruker Avance 300 (300 MHz), or Bruker DRX (300 MHz) instrument]; unless otherwise specified, measurements are performed at ambient temperature; the following abbreviations are used: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; dd, double doublet; ddd, doublet of double doublet; dt, double triplet; bs, broad signal.

(viii) Generally, the final product of Formula I is characterized by mass spectrometry (LCMS or UPLC) after liquid chromatography; UPLC is performed as follows: using a Waters UPLC system equipped with a Waters SQ mass spectrometer (column temperature 40°C, UV = 220-300 nm or 190-400 nm, mass spectrometry = ESI with positive/negative conversion) at a flow rate of 1 mL/min with a solvent system of 97% A + 3% B to 3% A + 97% B for 1.50 min (total run time including equilibration back to initial conditions is 1.70 min), wherein A = aqueous solution of 0.1% formic acid or 0.05% trifluoroacetic acid (for acid treatment) or aqueous solution of 0.1% ammonium hydroxide (for alkali treatment), and B = acetonitrile. For acid analysis, a Waters Acquity HSS T3 column (1.8 μm, 2.1 x 50 mm) was used; for base analysis, a Waters Acquity BEH C18 column (1.7 μm, 2.1 x 50 mm) was used. Alternatively, UPLC was performed as follows: using a Waters UPLC system equipped with a Waters SQ mass spectrometer (column temperature 30 °C, UV = 210-400 nm, mass spectrometry = ESI with positive/negative conversion) at a flow rate of 1 mL/min with a solvent gradient of 2% to 98% B for 1.5 min (total run time including equilibration back to starting conditions is 2 min), where A = 0.1% aqueous formic acid and B = 0.1% acetonitrile solution of formic acid (for acid treatment); or A = 0.1% aqueous ammonium hydroxide and B = acetonitrile (for base treatment). For acid analysis, a Waters Acquity HSS T3 column (1.8 μm, 2.1 x 30 mm) was used; for alkali analysis, a Waters Acquity BEH C18 column (1.7 μm, 2.1 x 30 mm) was used. LC-MS was performed as follows: using a Waters Alliance HT (2795) equipped with a Waters ZQ ESCi mass spectrometer and a Phenomenex Gemini-NX C18 column (5 μm, 110A, 2.1 x 50 mm), at a flow rate of 1.1 mL/min, with 95% A to 95% B for 4 min, held for 0.5 min, where A = 0.1% formic acid and B = 0.1% formic acid in acetonitrile solution (for acid treatment); or A = 0.1% ammonium hydroxide in aqueous solution and B = acetonitrile (for alkali treatment). In addition, LCMS was performed as follows: using a Shimadzu UFLC equipped with a Shimadzu LCMS-2020 mass spectrometer and a Waters HSS C18 (1.8 μm, 2.1 x 50 mm) or Shim-pack XR-ODS (2.2 μm, 3.0 x 50 mm) or Phenomenex Gemini-NX C18 (3 μm, 3.0 x 50 mm) column, at a flow rate of 0.7 mL/min (for Waters HSS C18, LCMS-20 ... The flow rate is 1.0 mL/min (for Shim-pack XR-ODS columns) or 1.2 mL/min (for Phenomenex Gemini-NXC18 columns), with 95% A to 95% B for 2.2 min, held for 0.6 min, where A = aqueous solution of 0.1% formic acid or 0.05% trifluoroacetic acid (for acid treatment), or aqueous solution of 0.1% ammonium hydroxide or 6.5 mM ammonium carbonate (for alkali treatment), and B = acetonitrile. Unless otherwise specified, the reported molecular ion corresponds to [M+H]+; for molecules with multiple isotopic modes (Br, Cl, etc.), unless otherwise specified, the reported value is the value obtained for the lowest isotopic mass.

(ix) Ion exchange purification is typically performed using an SCX-2 (Biotage) column.

(x) The purity of the intermediate was assessed by thin-layer chromatography, mass spectrometry, LCMS, UPLC/MS, HPLC (high performance liquid chromatography) and/or NMR analysis;

(xi) uses the following abbreviations: -

EtOAc: Ethyl acetate

Et ₂ O: Diethyl ether

DMSO: Dimethyl sulfoxide

LAH: Lithium aluminum hydride

LiHMDS: Lithium hexamethyldisilazane

MeOH: Methanol

TFA: Trifluoroacetic acid

MeCN: Acetonitrile

LCMS: Liquid Chromatography-Mass Spectrometry

rt or RT: Room temperature

aq: Aqueous solution

THF: Tetrahydrofuran

DCM: Dichloromethane

DMF: Dimethylformamide

HATU: (1-[bis(dimethylamino)methylene]-lH-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate)

TBAF: Tetrabutylammonium fluoride

AcOH: Acetic acid

DIAD: Diisopropyl azodicarbonate

Boc-Ala-OH: N-(tert-butoxycarbonyl)-L-alanine

Boc-Val-OH: N-(tert-butoxycarbonyl)-L-valine

HEPES: (4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid)

Example 1: (2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronic hexanoic acid dihydrochloride

Intermediate 1: (S)-4-(allyloxy)-2-amino-4-oxobutyrate

Under a _nitrogen atmosphere, L-aspartic acid (10.66 g, 80.09 mmol) was suspended in allyl alcohol (60.0 mL, 880 mmol). Trimethylchlorosilane (31.0 mL, 240 mmol) was added dropwise to the suspension via a syringe pump at a rate of 1 mL/min. The reaction mixture was stirred at room temperature for 16 h. The reaction mixture was diluted with ice-cold _Et₂O (100 mL) and the suspension was filtered. The solid was washed with ice-cold _Et₂O (3 x 15 mL) and dried to give (S)-4-(allyloxy)-2-amino-4-oxobutyrate salt as an amorphous white solid (intermediate 1, 12.7 g, 76% yield), which was then allowed to proceed without further purification. ¹ H NMR (300MHz, D ₂ O) δ 3.14 (2H, d), 4.25 (1H, t), 4.70 (2H, d), 5.26-5.48 (2H, m), 5.89-6.08 (1H, m); m/z: (ES ⁺ ) [M+H] ⁺ = 174.

Intermediate 2: (S)-4-allyl-1-tert-butyl-2-(benzyloxycarbonylamino)succinate

(S)-4-(allyloxy)-2-amino-4-oxobutyrate salt (intermediate 1, 11.58 g, 55.24 mmol) was dissolved in water (100 mL) and 1,4-dioxane (100 mL). Sodium carbonate (23.0 g, 220 mmol) was added in portions at room temperature and the reaction was stirred for 5 min. Benzyl chloroformate (8.3 mL, 58 mmol) was added dropwise to the reaction via a syringe pump at a rate of 1 mL/min. The biphasic reaction mixture was stirred at room temperature for 4 h. The crude reaction was quenched with concentrated aqueous HCl until pH < 1. The layers were separated and the aqueous layer was extracted with EtOAc (2 x 25 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to give a colorless oil. The crude carboxylic acid was dissolved in DCM (100 mL) and cooled to -78 °C in a pressure flask. Sulfuric acid (3.0 mL, 56 mmol) was added, followed immediately by pre-condensed isobutylene (66.0 mL, 710 mmol). The flask was sealed and stirred for 3 days, while the reaction was stopped in an ice bath. The reaction mixture was poured into a saturated sodium bicarbonate aqueous solution (200 mL) and stirred for 30 min. The layers were separated and the aqueous layer was extracted with DCM (2 x 20 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (S)-4-allyl-1-tert-butyl-2-(benzyloxycarbonylamino)succinate as a colorless oil (intermediate 2, 12.2 g, 61% yield). ¹ H NMR (300MHz, CDCl ₃ )δ1.47(9H,s),2.76-2.93(1H,dd),2.94-3.12(1H,dd),4.48-4.57(1H,m),4.60(2H,dq),5.14(2H,s),5.26(1H,dq),5.33(1H,dq),5.71(1H,br d), 5.91 (1H, ddt), 7.31-7.48 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =381.

Intermediate 3: 2-((S)-1-(benzyloxycarbonylamino)-2-tert-butoxy-2-oxoethyl)pent-4-enoic acid

A LiHMDS solution (1 M, in toluene, 100 mL, 100 mmol) was added to an oven-dried multineck flask and diluted with THF (50 mL) under a _N2 atmosphere. The solution was cooled to -78 °C, and (S)-4-allyl-1-tert-butyl-2-(benzyloxycarbonylamino)succinate (intermediate 2, 12.2 g, 33.5 mmol) was added dropwise to the reaction flask as a solution in THF (50 mL). The reaction was stirred at -78 °C for 80 min. Trimethylchlorosilane (17.0 mL, 133 mmol) was added, and the reaction was stirred at -78 °C for another 1 h. The reaction was then heated to 60 °C for 160 min. The reaction mixture was cooled to room temperature and quenched with 2 M HCl aqueous solution (67 mL). After vigorous stirring for 30 min, the layers were separated, and the aqueous layer was extracted with EtOAc (2 x 30 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to give 2-((S)-1-(benzyloxycarbonylamino)-2-tert-butyl-2-oxoethyl)pent-4-enoic acid (intermediate 3, 12.0 g, 99%) as an inseparable mixture of diastereomers in a ratio of approximately 1.7:1. ¹ HNMR (300MHz, CDCl ₃ )δ1.41 (3.4H, s) 1.43 (5.6H, s), 2.19-2.43 (1H, m), 2.44-2.66 (1H, m), 2.81-2.99 (0.65H, m), 3.08-3.25 (0.35 H, m), 4.48-4.63 (1H, m), 4.97-5.20 (4H, m), 5.52-5.71 (1H, m), 5.71-5.94 (1H, m), 7.25-7.39 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =364.

Intermediate 4: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate and

Intermediate 5: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate

2-((S)-1-(benzyloxycarbonylamino)-2-tert-butoxy-2-oxoethyl)pent-4-enoic acid (intermediate 3, 12.0 g, 33.0 mmol) was dissolved in THF (60 mL) and cooled to -10 °C under a _nitrogen atmosphere. N-methylmorpholine (3.7 mL, 34 mmol) was added and the reaction was stirred at -10 °C for 5 min, followed by the addition of ethyl chloroformate (3.2 mL, 33 mmol). The reaction mixture was heated to room temperature and stirred for 40 min. At 0 °C, the resulting suspension was filtered directly into a solution of sodium borohydride (3.0 g, 79 mmol) in water (60 mL). After the addition, the reaction mixture was heated to room temperature and stirred for 3 h. The reaction mixture was cooled to 0 °C and carefully quenched with 2 M HCl aqueous solution (20 mL). The layers were separated and the aqueous layer was extracted with EtOAc (2 x 25 mL). The combined organic compounds were dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl 2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4, 5.77 g, 50% yield) and (2S,3R)-tert-butyl 2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 5, 3.96 g, 34% yield) as colorless oils.

Intermediate 4: ^1H NMR (300MHz, _CDCl3 ) δ 1.46 (9H, s), 1.70-1.85 (1H, m), 1.85-1.99 (1H, m), 2.18-2.37 (1H, m), 3.26 (1H, t), 3.63 (1H, dd), 4.58 (1H, dd), 4.92-5.06 (2H, m), 5.10 (2H, s), 5.55 (1H, br d), 5.60-5.78 (1H, m), 7.26-7.39 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ ＝350.

Intermediate 5: ^1H NMR (300MHz, _CDCl3 ) δ 1.45 (9H, s), 2.03-2.12 (1H, m), 2.13-2.23 (2H, m), 3.65 (2H, qd), 4.34 (1H, br dd), 5.00-5.15 (4H, m), 5.62-5.90 (2H, m), 7.25-7.41 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ ＝350.

Intermediate 6: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hexyl- 5-Olefin ester

At 0 °C, triethylamine (7.4 mL, 53 mmol) and methanesulfonyl chloride (2.6 mL, 33 mmol) were added sequentially to a solution of (2S,3S)-tert-butyl 2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4, 4.61 g, 13.2 mmol) in DCM (100 mL). The reaction was heated to room temperature and stirred for 90 min. The crude mixture was diluted with DCM (25 mL) and washed sequentially with saturated sodium bicarbonate aqueous solution, water, and brine (25 mL each). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl 2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hex-5-enoate (intermediate 6, 5.3 g, 93% yield) as a pale yellow oil. ¹ H NMR (300MHz, CDCl ₃ ) δ1.46 (9H, s), 1.96-2.19 (2H, m), 2.36-2.58 (1H, m), 2.97 (3H, s), 4.00-4.23 (2H, m), 4.52 (1H, br d), 5.00-5.17(4H, m), 5.34(1H, br d), 5.60-5.83(1H, m), 7.27-7.37(5H, m); m/z: (ES ⁺ )[M+H] ⁺ =445.

Intermediate 7: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)-6- (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (0.25 g, 0.37 mmol) and bis(diphenylphosphine)methane (0.28 g, 0.74 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2) . The solid was dissolved in DCM (35 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (4.00 mL, 28.0 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hex-5-enoate (intermediate 6, 5.27 g, 12.3 mmol) was added to the reaction as a solution in DCM (30 mL), and the reaction mixture was stirred overnight. The reaction mixture was cooled to 0 °C and quenched with MeOH (6 mL) and water (50 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 15 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a yellow gel (intermediate 7, 5.84 g, 85% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.73(2H,t),1.20(12H,s),1.24-1.42(4H,m),1.45(9H,s),2.30-2.50(1H,m),2.97(3H,s),3.98(1H,t),4.18(1H,dd),4.50(1H,br d), 5.02-5.15 (2H, m), 5.35 (1H, br d), 7.27-7.42 (5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =573.

Intermediate 8: (2S,3R)-tert-butyl-3-(azidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl) Methyl-1,3,2-dioxaneborane-2-yl)hexanoate

Sodium azide (3.3 g, 51 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 7, 5.84 g, 10.5 mmol) in DMF (30 mL). The reaction mixture was heated to 55 °C and stirred for 16 h under a _nitrogen atmosphere. Another portion of sodium azide (200 mg, 3 mmol) was added, and the reaction mixture was stirred at 55 °C for another 4 h. The reaction mixture was cooled to room temperature and diluted with water (100 mL). The layers were separated and the aqueous layer was extracted with ether (3 x 35 mL). The combined organic matter was washed with brine (50 mL), dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl3-(azidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 8, 3.52 g, 67% yield) as a colorless oil. ¹ H NMR (300MHz, CDCl ₃ )δ0.73(2H,t),1.20(12H,s),1.22-1.40(4H,m),1.45(9H,s),2.04-2.20(1H,m),3.15-3.30(1H,m),3.31-3.43(1H,m),4.46(1H,br d), 5.10 (2H, s), 5.37 (1H, brd), 7.26-7.40 (5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =520.

Intermediate 9: (2S,3R)-tert-butyl-2-(tert-butoxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl 6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Pd/C (10% wt, 0.46 g, 0.43 mmol) and di-tert-butyl dicarbonate (2.50 mL, 10.8 mmol) were added to a solution of (2S,3R)-tert-butyl-3-(azidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 8, 2.16 g, 4.29 mmol) in EtOAc (15 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred at room temperature for 2 h. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc. The filtrate was concentrated into a turbid, colorless oil, which was then purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl2-(tert-butoxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 9, 1.65 g, 71% yield), which was a white foam. ¹ H NMR (300MHz, CDCl ₃ )δ0.67-0.73(2H, m), 0.95-1.16(2H, m), 1.20(12H, s), 1.37-1.47(29H, m), 2.00-2.20(1H, m), 2.36-2.56(1H, m), 3.31-3.57(1H, m), 4.34(1H, br d), 5.14 (1H, br d), 5.68 (1H, brs); m/z: (ES ^- )[M+HCOO ^- ] ^- =587.

Example 1: (2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronic acid dihydrochloride

HBr solution (33 wt%, in AcOH, 6.0 mL, 36 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(tert-butoxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 9, 2.2 g, 4.1 mmol) in DCM (32 mL), and the reaction was stirred at room temperature for 1 h. The reaction was diluted and concentrated with _Et₂O (10 mL). This step was repeated twice. The residue was dissolved in _Et₂O (40 mL) and 2M HCl aqueous solution (40 mL). Phenylboronic acid (0.989 g, 8.11 mmol) was added, and the reaction was stirred at room temperature for 2 h. The layers were separated and the aqueous layer was washed with _Et₂O (3 x 15 mL). The aqueous layer was lyophilized and purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 100% aqueous solution of MeCN) to give (2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronic hexanoic acid dihydrochloride as a yellow solid (Example 1, 0.713 g, 64% yield). ^¹H NMR (300 MHz, _D₂O ) δ 0.65–0.87 (2H, m), 1.32–1.56 (4H, m), 2.35–2.48 (1H, m), 3.12 (2H, qd), 4.09 (1H, d); m/z: ( ^ES⁺ )[ _MH₂O + H] ^⁺ = 187.

(2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronic acid dihydrochloride (Example 1, 713 mg, 2.57 mmol) was dissolved in MeOH (5 mL) and loaded onto a pre-equilibrated Porapak Rxn Cx (60 cc) ion exchange column. The resin was washed with MeOH (45 mL), followed by washing with a 5% _NH3 solution in MeOH (45 mL) to elute the product. The fraction containing the product was collected and condensed to give (2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronic acid (300 mg, 57% yield) as a white powdery residue, present as a 4:1 mixture of acyclic and cyclic coordination complexes. ¹ HNMR (300MHz, D ₂ O)δ0.49-0.92(2H,m),1.17-1.76(4H,m),2.03-2.18(0.8H,m),2.48-2.58(0.2H , m), 3.01 (1.6H, d), 3.16-3.26 (0.4H, m), 3.49 (0.8H, d), 3.71 (0.2H, d); m/z: (ES ⁺ )[MH ₂ O+H] ⁺ =187.

(2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronylhexanoic acid (95 mg, 0.47 mmol) was dissolved in MeOH (3 mL), and p-toluenesulfonic acid monohydrate (266 mg, 1.40 mmol) was added. The reaction mixture was stirred at room temperature for 20 h. The reaction mixture was concentrated and purified directly by reversed-phase chromatography (RediSep RfC18Aq, 0 to 100% aqueous solution of MeCN) to give (2S,3R)-2-amino-3-(aminomethyl)-6-dihydroxyboronylhexanoic acid dimethylsulfonate (180 mg, 71% yield) as a white solid. ¹ H NMIR (300MHz, D ₂ O) δ0.74-0.87 (2H, m), 1.38-1.61 (4H, m), 2.40 (6H, s), 2.45-2.48 (1H, m), 3.15(2H, qd), 4.01(1H, d), 7.27-7.50(4H, m), 7.63-7.79(4H, m); m/z: (ES ⁺ )[MH ₂ O-2TsOH+H] ⁺ =187.

Example 2: (2S,3R)-2-amino-6-dihydroxyboron-3-(morpholinomethyl)hexanoic acid

Intermediate 10: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)hex-5-enoate

At room temperature, morpholine (1.00 mL, 11.5 mmol) and potassium carbonate (829 mg, 6.00 mmol) were added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hex-5-enoate (intermediate 6, 513 mg, 1.20 mmol) in DMF (5 mL). The reaction mixture was heated to 80 °C and stirred for 16 h under a _nitrogen atmosphere. The reaction was cooled to room temperature and diluted with water (50 mL). The layers were separated and the aqueous layer was extracted with _Et₂O (3 x 25 mL). The combined organic matter was dried over _MgSO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)hex-5-enoate as a colorless oil (intermediate 10, 285 mg, 57% yield). ^¹H NMR (300 MHz, _CDCl₃ ) δ 1.45 (9H, s), 1.63–2.61 (9H, m), 3.54–3.79 (4H, m), 4.44 (1H, br d), 4.95–5.16 (4H, m), 5.63–5.87 (1H, m), 7.05 (1H, br d), 7.25–7.39 (5H, m); m/z: ( ^ES⁺ )[M+H] ^⁺ = 419.

Intermediate 11: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)-6-(4,4,5,5- Tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (14 mg, 0.020 mmol) and bis(diphenylphosphine)methane (16 mg, 0.040 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (3 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.22 mL, 1.5 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)hex-5-enoate (intermediate 10,285 mg, 0.680 mmol) was added to the reaction as a solution in DCM (2 mL), and the reaction mixture was stirred overnight. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 11,228 mg, 61% yield). ¹ H NMR (300MHz, CDCl ₃ ) δ0.64-0.83 (2H, br t), 1.20 (12H, s), 1.28-1.53 (13H, m), 1.93-2.63 (4H, m), 3.06-4.00 (4H, m), 4.26-4.61 (1H, m), 4.99-5.18 (2H, m), 7.26-7.39 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =547.

Example 2: (2S,3R)-2-amino-6-dihydroxyboron-3-(morpholinomethyl)hexanoic acid

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(morpholinomethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 11,228 mg, 0.420 mmol) was dissolved in 6M HCl aqueous solution (4.0 mL), and the solution was heated to 100 °C for 16 h. The reaction was cooled to room temperature, diluted with water (5 mL), and washed with _Et₂O (3 x 10 mL). The aqueous layer was lyophilized and purified by ion exchange chromatography (PoraPak Rxn CX 20 cc column). The resin was washed with MeOH (15 mL), followed by washing with 5% _NH₃ in MeOH solution (15 mL) to elute the product. The fraction containing the product was collected and concentrated to give (2S,3R)-2-amino-6-dihydroxyboron-3-(morpholinomethyl)hexanoic acid as a white solid (Example 2, 69 mg, 60% yield). ^¹H NMR (300 MHz, _D₂O ) δ 0.72–0.88 (2H, m), 1.24–1.38 (1H, m), 1.40–1.58 (3H, m), 2.19–2.34 (1H, m), 2.43–2.58 (4H, m), 2.62–2.77 (2H, m), 3.71–3.85 (4H, m), 3.88 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 275.

Example 3: (2S,3R)-2-amino-6-dihydroxyboron-3-(piperidin-1-ylmethyl)hexanoic acid

Intermediate 12: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)hex-5-enoic acid ester

Oxaloyl chloride solution (2M, 0.72 mL, 1.4 mmol in DCM) was added to an oven-dried flask, diluted with DCM (3 mL), and cooled to -78 °C under a _N2 atmosphere. DMSO (0.15 mL, 2.2 mmol) was added dropwise, and the reaction was stirred at -78 °C for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4, 250 mg, 0.72 mmol) was slowly added as a solution in DCM (3 mL), and the reaction was stirred at -78 °C for 30 min. N,N-diisopropylethylamine (0.50 mL, 2.9 mmol) was added, and the reaction was stirred at -78 °C for 1 h, then heated to 0 °C and stirred for another 15 min. The reaction mixture was quenched with a saturated _NaHCO3 aqueous solution (10 mL) and diluted with DCM (50 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 20 mL). The combined organic matter was dried over anhydrous _Na₂SO₄ , filtered, and concentrated to approximately 8 mL of solvent. The crude aldehyde was treated with piperidine (0.14 mL, 1.4 mmol), sodium triacetoxyborohydride ₍ 379 mg, 1.79 mmol), and acetic acid (0.041 mL, 0.72 mmol), and the resulting suspension was stirred at room temperature for 16 h. The reaction mixture was diluted with DCM (50 mL) and saturated _NaHCO₃ aqueous solution (10 mL), and the layers were separated. The aqueous layer was extracted with DCM (2 x 10 _mL ). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)hex-5-enoate (intermediate 12, 269 mg, 90%) as a colorless oil. ^¹H NMR (300 MHz, _CDCl₃ ) δppm 1.39–1.53 (15H, m), 1.86–1.94 (1H, m), 2.07–2.46 (8H, m), 4.32 (1H, d), 5.03–5.15 (4H, m), 5.73–5.85 (1H, m), 7.26–7.35 (5H, m), 7.90 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 417.

Intermediate 13: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)-6-(4,4,5, 5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (16 mg, 0.022 mmol) and bis(diphenylphosphine)methane (24 mg, 0.062 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (3 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.20 mL, 1.4 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)hex-5-enoate (intermediate 12,265 mg, 0.636 mmol) was added to the reaction as a solution in DCM (3 mL), and the reaction mixture was stirred overnight. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 13,240 mg, 69% yield). m/z: (ES ⁺ )[M+H] ⁺ = 545.

Example 3: (2S,3R)-2-amino-6-dihydroxyboron-3-(piperidin-1-ylmethyl)hexanoic acid

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(piperidin-1-ylmethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 13,240 mg, 0.44 mmol) was dissolved in 6 M HCl aqueous solution (12 mL) and the solution was heated to 100 °C for 16 h. The reaction mixture was cooled to room temperature, diluted with _H₂O (25 mL) and washed with EtOAc (2 x 15 mL). The aqueous layer was concentrated under reduced pressure and the resulting residue was purified by reversed-phase chromatography (RediSepRfC18, 0 to 50% aqueous acetonitrile) to give (2S,3R)-2-amino-6-dihydroxyboron-3-(piperidin-1-ylmethyl)hexanoic acid as a white solid (Example 3, 79 mg, 36% yield). The obtained material was a 5.7:1 mixture of the title product and diastereomeric C3. ^¹H NMR (300 MHz, _D₂O ) δ 0.81–0.84 (2H, m), 1.42–1.58 (5H, m), 1.75–1.86 (3H, m), 1.93–1.99 (2H, m), 2.49 (0.2H, s, br), 2.62–2.64 (0.76H, m), 2.92–3.05 (2H, m), 3.16–3.43 (2H, m), 3.53–3.66 (2H, m), 4.15 (0.8H, d), 4.23 (0.2H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 273.

Example 4: (2S,3R)-2-amino-6-dihydroxyboron-3-((methylamino)methyl)hexanoic acid

Intermediate 14: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino) methyl 5-hexanoate

Oxaloyl chloride solution (2M, 0.57 mL, 1.1 mmol in DCM) was added to an oven-dried flask, diluted with DCM (2 mL), and cooled to -78 °C under a _N2 atmosphere. DMSO (0.12 mL, 1.7 mmol) was added dropwise, and the reaction was stirred at -78 °C for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4, 200 mg, 0.57 mmol) was slowly added as a solution in DCM (3 mL), and the reaction was stirred at -78 °C for 30 min. N,N-diisopropylethylamine (0.40 mL, 2.3 mmol) was added, and the reaction was stirred at -78 °C for 1 h, then heated to 0 °C and stirred for another 15 min. The reaction mixture was quenched with a saturated _NaHCO3 aqueous solution (10 mL) and diluted with DCM (20 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over anhydrous _Na₂SO₄ , filtered, and concentrated to approximately 8 mL of solvent. The crude aldehyde was treated with 1-(4-methoxyphenyl)-N-methylmethylamine (173 mg, 1.14 mmol), sodium triacetoxyborohydride ₍ 415 mg, 1.96 mmol), and acetic acid (0.033 mL, 0.57 mmol), and the resulting suspension was stirred at room temperature for 4 h. The reaction mixture was diluted with DCM (30 mL) and saturated _NaHCO₃ aqueous solution (20 mL), and the layers were separated. The aqueous layer was extracted with DCM (3 x 30 mL). The combined organic matter was dried over _{anhydrous Na₂SO₄} , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino)methyl)hex-5-enoate (intermediate 14, 221 mg, 80% yield), which was a colorless oil. m/z: (ES ⁺ )[M+H] ⁺ = 483.

Intermediate 15: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino) (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (11 mg, 0.017 mmol) and bis(diphenylphosphine)methane (17 mg, 0.046 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (3 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.15 mL, 1.0 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino)methyl)hex-5-enoate (intermediate 14, 220 mg, 0.46 mmol) was added to the reaction as a solution in DCM (3 mL), and the reaction mixture was stirred overnight. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 15,182 mg, 65% yield). m/z: (ES ⁺ )[M + H] ⁺ ＝ 610.

Example 4: (2S,3R)-2-amino-6-dihydroxyboron-3-((methylamino)methyl)hexanoic acid

Pd/C (10% wt, 280 mg, 0.26 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((4-methoxybenzyl)(methyl)amino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 15, 162 mg, 0.27 mmol) in MeOH (10 mL). The suspension was stirred for 4 h at room temperature under a hydrogen atmosphere (balloon, flask evacuated and backfilled with hydrogen 3 times). The reaction mixture was diluted with MeOH, filtered through diatomaceous earth, and the filtrate was concentrated to dryness. The resulting residue was dissolved in 6 M HCl aqueous solution (10 mL) and heated to 100 °C for 2 h. The reaction mixture was cooled to room temperature, diluted with _H₂O (10 mL), and washed with DCM (2 x 15 mL). The aqueous layer was concentrated under reduced pressure, and the resulting residue was purified by reversed-phase chromatography (RediSep Rf C18, 0 to 30% aqueous acetonitrile) to give (2S,3R)-2-amino-6-dihydroxyboron-3-((methylamino)methyl)hexanoic acid as a white solid (Example 4, 33 mg, 43% yield). The material obtained was a 6.1:1 mixture of the title product and diastereomeric C3. ¹ H NMR (300MHz, D ₂ O)δ0.73-0.81(2H,m),1.35-1.55(4H,m),2.27-2.45(1H,m),2.74(3H,s),3.05-3.22( 1.82H, m), 3.29-3.37 (0.12H, m), 3.85-3.93 (0.81H, m), 3.99-4.03 (0.12H, m); m/z: (ES ⁺ )[M+H] ⁺ =219.

Example 5: (2S,3R )-2-amino-6-dihydroxyboron-3-((dimethylamino)methyl)hexanoic acid

Intermediate 16: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((dimethylamino)methyl)hex-5-ene esters

Oxaloyl chloride solution (2M, 2.54 mL, 5.08 mmol in DCM) was added to an oven-dried flask, diluted with 10 mL of DCM, and cooled to -78 °C under a _N2 atmosphere. DMSO (0.54 mL, 7.6 mmol) was added dropwise, and the reaction was stirred at -78 °C for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4,888 mg, 2.54 mmol) was slowly added as a solution in 10 mL of DCM, and the reaction was stirred at -78 °C for 30 min. N,N-diisopropylethylamine (0.50 mL, 2.9 mmol) was added, and the reaction was stirred at -78 °C for 1 h, then heated to 0 °C and stirred for another 15 min. The reaction mixture was quenched with ₂₀ mL of saturated NaHCO3 aqueous solution and diluted with 40 mL of DCM. The layers were separated and the aqueous layer was extracted with DCM (2 x 20 mL). The combined organic matter was dried over anhydrous _Na₂SO₄ , filtered, and concentrated to dryness. A portion of the crude aldehyde (294 mg, 0.847 mmol) was dissolved in DCM (20 mL), and dimethylamine solution (2 M, in THF, 1.70 _mL , 3.40 mmol) was added, followed by sodium triacetoxyborohydride (448 mg, 2.12 mmol) and acetic acid (0.048 mL, 0.85 mmol). The resulting suspension was stirred at room temperature for 15 h. The reaction mixture was diluted with DCM (50 mL) and saturated _NaHCO₃ aqueous solution (10 mL), and the layers were separated. The aqueous layer was extracted with DCM (2 x 10 _mL ). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((dimethylamino)methyl)hex-5-enoate as a colorless oil (intermediate 16, 253 mg, 79% yield). m/z: (ES ⁺ )[M+H] ⁺ = 377.

Intermediate 17: (4R,5S)-5-(benzyloxycarbonylamino)-6-tert-butoxy-4-((dimethylamino)methyl)- 6-Oxohexylboronic acid

Bis(1,5-cyclooctadiene)diiridium(I) chloride (16 mg, 0.025 mmol) and bis(diphenylphosphine)methane (26 mg, 0.067 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (3 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.22 mL, 1.5 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((dimethylamino)methyl)hex-5-enoate (intermediate 16,253 mg, 0.672 mmol) was added to the reaction as a solution in DCM (3 mL), and the reaction mixture was stirred overnight. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (4R,5S)-5-(benzyloxycarbonylamino)-6-tert-butoxy-4-((dimethylamino)methyl)-6-oxohexylboronic acid (intermediate 17,223 mg, 79% yield). m/z: (ES ⁺ )[M+H] ⁺ = 422.

Example 5: (2S,3R)-2-amino-6-dihydroxyboron-3-((dimethylamino)methyl)hexanoic acid

(4R,5S)-5-(benzyloxycarbonylamino)-6-tert-butoxy-4-((dimethylamino)methyl)-6-oxohexylboronic acid (intermediate 17,223 mg, 0.528 mmol) was dissolved in 15 mL of 6 M HCl aqueous solution and the solution was heated to 100 °C for 20 h. The reaction mixture was cooled to room temperature, and the solid was removed by filtration and washed with water. The aqueous filtrate was washed with DCM (3 x 20 mL) and concentrated under reduced pressure. The resulting residue was dissolved in 3 mL of MeOH and purified by ion exchange chromatography (PoraPak Rxn CX 20 cc column). The desired product was eluted from the column using 20 mL of 5% ammonia in MeOH solution. The fraction containing the product was collected and concentrated to give (2S,3R)-2-amino-6-dihydroxyboron-3-((dimethylamino)methyl)hexanoic acid as a white solid (Example 5, 68 mg, 56% yield). The obtained material was a 10:1 mixture of the title product and diastereomeric C3. ^¹H NMR (300 MHz, _D₂O ) δ 0.77 (2H, m), 1.25–1.48 (4H, m), 2.25 (1H, m), 2.69 (6H, s), 2.85–3.05 (2H, m), 3.62 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 233.

Example 6: (2S,3R)-2-amino-6-dihydroxyboron-3-(guanidinomethyl)hexanoic acid dihydrochloride

Intermediate 18: tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-3-(((2,2,10,10-tetramethyl- 4,8-Dioxo-3,9-dioxa-5,7-diazaundecane-6-ylidene)amino)methyl)hex-5-enoate

(2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4,500 mg, 1.43 mmol) was dissolved in anhydrous toluene (14 mL). Triphenylphosphine (826 mg, 3.15 mmol) and 1,3-bis(tert-butoxycarbonyl)guanidine (742 mg, 2.86 mmol) were added, and the solution was cooled to 0 °C. DIAD (637 mg, 3.15 mmol) was added dropwise, and the reaction mixture was heated to room temperature, then further heated to 100 °C for 30 min. The reaction mixture was cooled to room temperature and washed with water (5 _mL ). The organic layer was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-3-(((2,2,10,10-tetramethyl-4,8-dioxo-3,9-dioxa-5,7-diazaundecane-6-ylidene)amino)methyl)hex-5-enolate (intermediate 18, 300 mg, 35.5%). ¹ H NMR (300MHz, CDCl ₃ ) δ1.40 (9H, s), 1.49-1.61 (18H, m), 2.11-2.50 (3H, m), 3.75-4.05 (2H, m), 4.21 (1H, br d), 4.97-5.17(4H, m), 5.67-5.91(1H, m), 6.20(1H, br s), 7.27-7.40(5H, m), 9.01-9.60(2H, m); m/z: (ES ⁺ )[M+H] ⁺ =591.

Intermediate 19: tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-6-(4,4,5,5-tetramethyl-1,3, 2-Dioxacyclopentaborane-2-yl)-3-(((2,2,10,10-tetramethyl-4,8-dioxo-3,9-dioxa-5,7-diaza) Undecane-6-ylidene)amino)methyl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (13 mg, 0.019 mmol) and bis(diphenylphosphine)methane (16 mg, 0.042 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2) . The solid was dissolved in DCM (8 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.18 mL, 1.3 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. Tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-3-(((2,2,10,10-tetramethyl-4,8-dioxo-3,9-dioxa-5,7-diazaundecan-6-ylidene)amino)methyl)hex-5-enolate (intermediate 18, 300 mg, 0.51 mmol) was added to the reaction as a solution in DCM (2 mL), and the reaction was stirred at room temperature for 24 h. The reaction mixture was concentrated to dryness and purified directly by silica gel chromatography (hexane/EtOAc) to give tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)-3-(((2,2,10,10-tetramethyl-4,8-dioxo-3,9-dioxa-5,7-diazaundecan-6-ylidene)amino)methyl)hexanoate as a colorless oil (intermediate 19, 190 mg, 52% yield). ¹ H NMR (300MHz, CDCl ₃ )δ075 (2H, t), 1.12-1.24 (14H, m), 1.33-1.42 (10H, m), 1.46 (9H, s), 1.48-1.55 (10H, m), 2.23-2.42 (1H, m), 3.54-3.87 (1H, m ), 3.91-4.09(1H, m), 4.13-4.27(1H, m), 4.99-5.19(2H, m), 6.12-6.50(1H, m), 7.27-7.40(5H, m), 9.11-9.55(2H, m); m/z: (ES ⁺ )[M+H] ⁺ =719.

Example 6: (2S,3R)-2-amino-6-dihydroxyboron-3-(guanidinomethyl)hexanoic acid dihydrochloride

Tert-butyl(2S,3R)-2-(((benzyloxy)carbonyl)amino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)-3-(((2,2,10,10-tetramethyl-4,8-dioxo-3,9-dioxa-5,7-diazaundecane-6-ylidene)amino)methyl)hexanoate (intermediate 19, 45 mg, 0.063 mmol)) was dissolved in 6M HCl aqueous solution (2.08 mL, 12.5 mmol), and the reaction mixture was heated to 90 °C for 30 min. The reaction mixture was cooled to 70 °C and stirred for 1 h. The reaction mixture was cooled to room temperature, diluted with water (2 mL), and extracted with EtOAc (3 x 1 mL). The aqueous layer was freeze-dried to give (2S,3R)-2-amino-6-dihydroxyboron-3-(guanidinomethyl)hexanoic acid dihydrochloride as a white solid (Example 6, 10 mg, 50% yield). ^¹H NMR (300 MHz, _D₂O ) δ 0.80 (2H, br d), 1.37–1.62 (4H, m), 2.41 (1H, br d), 3.34 (2H, dd), 4.09 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 247.

Example 7: (2S,3R)-2-amino-6-dihydroxyboron-3-(ureomethyl)hexanoic acid

Intermediate 20: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-di) oxacyclopentaborane-2-yl)-3-(ureomethyl)hexanoate

Pd/C (10% wt, 220 mg, 0.21 mmol) was added to a solution of (2S,3R)-tert-butyl-3-(azidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 8, 485 mg, 1.04 mmol) and trimethylsilyl isocyanate (0.35 mL, 2.6 mmol) in EtOAc (40 mL). The mixture was evacuated and backfilled with nitrogen three times, then evacuated and backfilled with hydrogen. The suspension was stirred at room temperature for 3 h under a hydrogen atmosphere. A second portion of trimethylsilyl isocyanate (0.15 mL, 1.1 mmol) was added, and the suspension was stirred again at room temperature for 20 min. The reaction mixture was diluted with DCM, filtered through diatomaceous earth, and the filtrate was concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)-3-(ureomethyl)hexanoate as a white solid (intermediate 20, 242 mg, 48% yield). m/z: (ES ⁺ )[M+H] ⁺ = 486.

Example 7: (2S,3R)-2-amino-6-dihydroxyboron-3-(ureomethyl)hexanoic acid

Trifluoroacetic acid (6.00 mL, 77.9 mmol) was slowly added to a stirred solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)-3-(ureomethyl)hexanoate (intermediate 20, 242 mg, 0.466 mmol) in DCM (6 mL), and the reaction was stirred at room temperature for 6 h. The solution was concentrated under reduced pressure, and the resulting residue was dissolved in 1 M HCl aqueous solution (5 mL) and _Et₂O (5 mL). Phenylboronic acid (117 mg, 0.96 mmol) was added, and the clear biphasic solution was stirred at room temperature for 16 h. The reaction mixture was diluted with _Et₂O and water, and the layers were separated. The aqueous layer was washed with _Et₂O (2 x 30 mL) and then lyophilized. The crude material was purified by reversed-phase chromatography (RediSepRfC18, 0 to 50% aqueous acetonitrile) to give (2S,3R)-2-amino-6-dihydroxyboron-3-(ureidomethyl)hexanoic acid as a white solid (Example 7, 5.0 mg, yield 4%).

¹ H NMR (300MHz, D ₂ O) δ 0.77-0.82 (2H, m), 1.24-1.49 (4H, m), 2.11-2.20 (1H, m), 3.07-3.22 (2H, m), 3.71 (1H, d); m/z: (ES ⁺ ) [M+H] ⁺ = 248.

Example 8: (2S,3R)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyborylhexyl acid

Intermediate 21: (2S,3R)-tert-butyl2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(tri-) Methylsilyl)ethylsulfonamide)methyl)hexyl-5-enoate

(2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 4,938 mg, 2.68 mmol) and tert-butyl((2-(trimethylsilyl)ethyl)sulfonyl)carbamate (1.1 g, 3.9 mmol) were dissolved in THF (10 mL) and cooled to 0 °C. Triphenylphosphine (1.06 mg, 4.03 mmol) and DIAD (1.1 mL, 5.7 mmol) were added, and the reaction was stirred for 16 h while slowly heated to room temperature. The reaction was quenched with saturated sodium bicarbonate aqueous solution (10 mL), and the layers were separated. The aqueous layer was extracted with EtOAc (2 x 10 mL). The combined organic layers were dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(trimethylsilyl)ethylsulfonamide)methyl)hex-5-enoate (intermediate 21, 1.56 g, 95%), which was a colorless gel. ¹ H NMR (300MHz, CDCl ₃ )δ0.04(9H, s), 0.81-0.99(2H, m), 1.46(9H, s), 1.49(9H, m), 2.05-2.29(2 H, m), 2.44-2.58 (1H, m), 3.34-3.54 (2H, m), 3.55-3.81 (2H, m), 4.35 (1H, br dd), 4.93-5.20 (4H, m), 5.42 (1H, br d), 5.69-5.96 (1H, m), 7.26-7.45 (5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =630.

Intermediate 22: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl) Hex-5-enoate

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(trimethylsilyl)ethylsulfonamide)methyl)hex-5-enoate (intermediate 21, 1.40 g, 2.28 mmol)) was dissolved in TBAF solution (1 M, in THF, 12.0 mL, 12.0 mmol), and the resulting solution was stirred at room temperature for 16 h. The reaction mixture was diluted with _Et₂O (40 mL) and washed successively with water (3 x 25 mL) and saturated sodium bicarbonate aqueous solution (20 mL). The organic layer was dried over _MgSO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)hex-5-enoate as a colorless oil (intermediate 22,576 mg, 56% yield). ¹ H NMR (300MHz, CDCl ₃ )δ1.43(9H,s),1.44(9H,s),1.74-1.88(1H,m),1.89-2.00(1H,m),2.17-2.30(1H,m),2.41 -2.60(1H,m),3.38-3.62(1H,m),4.46(1H,dd),4.98-5.08(2H,m),5.09(2H,s),5.40(1H,br d), 5.52-5.88(2H, m), 7.27-7.38(5H, m); m/z: (ES ⁺ )[M+H] ⁺ =449.

Intermediate 23: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)- 6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (13 mg, 0.065 mmol) and bis(diphenylphosphine)methane (49 mg, 0.13 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (4 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.50 mL, 3.5 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)hex-5-enoate (intermediate 22,576 mg, 1.28 mmol) was added to the reaction as a solution in DCM (3 mL), and the reaction was stirred at room temperature for 3 days. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (15 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate, an intermediate (23,424 mg, 57% yield), as a pale yellow gel. ¹ H NMR (300MHz, CDCl ₃ )δ0.57-0.81(2H, m), 0.94-1.15(2H, m), 1.19(12H, s), 1.28-1.59(20H, m), 2.05-2.23 (1H, m), 2.40-2.57 (1H, m), 3.39-3.60 (1H, m), 4.43 (1H, dd), 5.08 (2H, s), 5.41 (1H, br d), 5.53-5.78 (1H, m), 7.27-7.38 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =577.

Intermediate 24: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

At 0 °C, HCl solution (4 M, in dioxane, 1.5 mL, 6.0 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxane-2-yl)hexanoate (intermediate 23,424 mg, 0.740 mmol) in dioxane (1.5 mL). The reaction was stirred for 6 h while slowly heated to room temperature. The solution was concentrated to give a yellow gel, which was used directly without further purification. In a separating flask, HATU (619 mg, 1.63 mmol) was added to a solution of Boc-L-Val-OH (354 mg, 1.63 mmol) in DMF (3.5 mL), and the reaction was stirred at room temperature for 10 min. The crude amine was dissolved in DMF (3.5 mL) and added to a second reaction flask. N,N-diisopropylethylamine (0.45 mL, 2.6 mmol) was added, and the reaction was stirred at room temperature for 16 h. The reaction mixture was diluted with EtOAc (15 mL) and washed with 1 M HCl aqueous solution (60 mL) and 5% lithium chloride aqueous solution (10 mL). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to give (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a pale yellow gel (intermediate 24,476 mg, 95% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.59-0.82(2H,m),0.87-0.98(6H,m),1.18(12H,s),1.28-1.55(22H,m),2.07-2.24(2H,m),2.31-2.51 (1H, m), 3.38-3.54 (1H, m), 3.74-3.89 (1H, m), 3.89-4.06 (1H, m), 4.35 (1H, dd), 5.08 (2H, s), 5.50 (1H, br d), 6.92 (1H, br s), 7.26-7.37 (5H, m); m/z: (ES-)[M+HCOOdin=720.

Example 8: (2S,3R)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyborylhexyl acid

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 24,476 mg, 0.700 mmol)) was dissolved in HBr solution (33 wt%, in AcOH, 3.5 mL, 21 mmol), and the reaction was stirred at room temperature for 20 min. The reaction was diluted and concentrated with _Et₂O (10 mL). This step was repeated twice. The resulting residue was dissolved in 2 M HCl aqueous solution (5 mL) and _Et₂O (5 mL). Phenylboronic acid (172 mg, 1.41 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion-exchange chromatography (HyperSep Retain CX column). The desired product was eluted from the column using a 5% ammonia solution of MeOH (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 8, 46 mg, 21% yield). ¹ H NMR (300MHz, D ₂ O) δ0.70-0.85 (2H, m), 0.96 (6H, dd), 1.24-1.59 (4H, m), 2.00 (1H, sextet), 2.16-2.35 (1H, m), 3.23-3.43 (3H, m), 3.68 (1H, d); m/z: (ES-)[MH]-=302.

Example 9: (2S,3R)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronic acid

Intermediate 25: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

At 0 °C, HCl solution (4 M, in dioxane, 4.40 mL, 17.6 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxane-2-yl)hexanoate (intermediate 23, 1.27 g, 2.20 mmol) in dioxane (1.5 mL). The reaction was stirred for 4.5 h while being slowly heated to room temperature. The solution was concentrated to give a yellow gel, which was used directly without further purification. In a separating flask, HATU (619 mg, 1.63 mmol) was added to a solution of Boc-Abu-OH (335 mg, 1.65 mmol) in DMF (5 mL), and the reaction was stirred at room temperature for 10 min. The crude amine from the previous operation was divided into two equal portions (assumed to be 524 mg, 1.10 mmol), and one portion was dissolved in DMF (5 mL) and added to the second reaction flask. N,N-diisopropylethylamine (0.60 mL, 3.4 mmol) was added, and the reaction was stirred at room temperature for 2 h. The reaction mixture was diluted with EtOAc (15 mL) and washed with 1 M HCl aqueous solution (60 mL) and 5% lithium chloride aqueous solution (10 mL). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)butamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless gel (intermediate 25,516 mg, 71% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.58-0.82(2H,m),0.93(3H,t),1.19(12H,s),1.38-1.45(22H,m),1.60-1.76(1H,m),1.77-1.97(2H,m),2.10-2.26 (1H, m), 2.40 (1H, dt), 3.78-3.90 (1H, m), 4.03-4.16 (1H, m), 4.34 (1H, dd), 5.08 (2H, s), 5.15-5.24 (1H, m), 5.48 (1H, br d), 7.27-7.39 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ ＝662.

Example 9: (2S,3R)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronic acid

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)butamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 25,516 mg, 0.780 mmol)) was dissolved in HBr solution (33 wt%, in AcOH, 4.0 mL, 24 mmol), and the reaction was stirred at room temperature for 20 min. The reaction was diluted and concentrated with _Et₂O (10 mL). This step was repeated twice. The resulting residue was dissolved in 2M HCl aqueous solution (5 mL) and _Et₂O (7 mL). Phenylboronic acid (190 mg, 1.6 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion exchange chromatography (Silicycle SPE-R51230B-20X column). The desired product was eluted from the column using a 5% ammonia MeOH solution (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronylhexanoic acid as a white solid (Example 9, 101 mg, 45% yield). ¹ H NMR (300MHz, D ₂ O)δ0.66-0.85(2H,m),0.92(3H,t),1.24-1.55(4H,m),1.65-1.83(2H,m) , 2.16-2.31(1H, m), 3.24-3.39(2H, m), 3.56(1H, t), 3.65(1H, d); m/z: (ES ⁺ )[M+H] ⁺ =290.

Example 10: (2S,3R )-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid

Intermediate 26: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

At 0 °C, a solution of HCl (4 M, in dioxane, 0.34 mL, 1.4 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 23,375 mg, 0.650 mmol) in dioxane (2 mL), and the reaction was stirred at 0 °C for 50 min. Another portion of HCl (4 M, in dioxane, 0.34 mL, 1.4 mmol) was added, and the reaction was stirred for another 1 h. Another portion of HCl (4 M, in dioxane, 0.70 mL, 2.7 mmol) was added, and the reaction was stirred for 1 h, then placed in a -20 °C freezer for 16 h. The reaction was allowed to warm to room temperature and stirred for 20 min. The solution was concentrated to obtain a yellow gel, which was used directly without further purification. In a separating flask, HATU (544 mg, 1.43 mmol) was added to a solution of Boc-Ala-OH (271 mg, 1.43 mmol) in DMF (3 mL), and the reaction was stirred at room temperature for 10 min. The crude amine was dissolved in DMF (3 mL) and added to a second reaction flask. N,N-diisopropylethylamine (0.38 mL, 2.2 mmol) was added, and the reaction was stirred at room temperature for 2 h. The reaction mixture was diluted with EtOAc (15 mL) and washed with 1 M HCl aqueous solution (60 mL) and 5% lithium chloride aqueous solution (30 mL). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to obtain (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)propamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate, an intermediate of 26,268 mg, 64% yield. ¹ H NMR (300MHz, CDCl ₃ )δ0.55-0.84(2H,m),0.96-1.27(14H,m),1.30-1.52(23H,m),2.07-2.27(1H,m),2.34-2.63(1H,m),2.74-2.99(1 H, m), 3.61-3.93 (1H, m), 3.99-4.23 (1H, m), 4.23-4.42 (1H, m), 4.90-5.24 (3H, m), 5.41-5.60 (1H, m), 7.33 (5H, br s); m/z: (ES ⁺ )[M+H] ⁺ =648.

Example 10: (2S,3R)-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)propamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 26,268 mg, 0.410 mmol)) was dissolved in HBr solution (33 wt%, in AcOH, 2.0 mL, 12 mmol), and the reaction was stirred at room temperature for 20 min. The reaction mixture was diluted with _Et₂O (5 mL) and concentrated. This step was repeated twice. The resulting residue was dissolved in 2 M HCl aqueous solution (2.5 mL) and _Et₂O (5 mL). Phenylboronic acid (100 mg, 0.83 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion-exchange chromatography (HyperSep Retain CX column). The desired product was eluted from the column using a 5% ammonia solution of MeOH (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 10, 45 mg, 39% yield). ¹ H NMR (300 MHz, D ₂ O) δ0.63-0.84 (2H, m), 1.20-1.55 (7H, m), 2.14-2.25 (1H, m), 3.20-3.36 (2H, m), 3.62 (1H, d), 3.74 (1H, q); m/z (ES ⁺ ) [M+H] ⁺ =276.

Example 11: (2S,3R)-3-(acetamidomethyl)-2-amino-6-dihydroxyboronic acid

Intermediate 27: (2S,3R)-tert-butyl-3-(acetamidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5, 5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

At 0 °C, HCl solution (4 M, in dioxane, 4.40 mL, 17.6 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxane-2-yl)hexanoate (intermediate 23, 1.27 g, 2.20 mmol) in dioxane (1.5 mL). The reaction was stirred for 4.5 h while being slowly heated to room temperature. The solution was concentrated to give a yellow gel, which was used directly without further purification. The crude amine was divided into two equal portions (assumed to be 524 mg, 1.10 mmol), and one portion was dissolved in DCM (5 mL). Triethylamine (0.40 mL, 2.9 mmol) was added, and the reaction was stirred at room temperature for 10 min. Acetyl chloride (0.10 mL, 1.4 mmol) was added, and the reaction was stirred for another 2 h. The reaction was quenched with water (15 mL) and diluted with DCM (20 mL). The layers were separated, and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic layers were washed with saturated sodium bicarbonate aqueous solution (20 mL), dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to give (2S,3R)-tert-butyl-3-(acetamidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 27,538 mg, 94% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.55-0.81(2H, m), 1.19(12H, s), 1.26-1.59(13H, m), 1.98(3H, s), 2.07-2.20( 1H, m), 2.33-2.45 (1H, m), 3.84 (1H, ddd), 4.36 (1H, dd), 5.08 (2H, s), 5.49 (1H, br d), 6.76-6.90 (1H, m), 7.26-7.40 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =519.

Example 11: (2S,3R)-3-(acetamidomethyl)-2-amino-6-dihydroxyboronic acid

(2S,3R)-tert-butyl-3-(acetamidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 27,538 mg, 1.04 mmol)) was dissolved in HBr solution (33 wt%, in AcOH, 5.0 mL, 30 mmol), and the reaction was stirred at room temperature for 20 min. The reaction was diluted and concentrated with _Et₂O (10 mL). This step was repeated twice. The resulting residue was dissolved in 2 M HCl aqueous solution (7 mL) and _Et₂O (7 mL). Phenylboronic acid (253 mg, 2.08 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion-exchange chromatography (Silicycle SPE-R51230B-20X column). The desired product was eluted from the column using a 5% ammonia solution of MeOH (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-3-(acetamidomethyl)-2-amino-6-dihydroxyboronic acid as a white solid (Example 11, 84 mg, 33% yield). ¹ H NMR (300MHz, D ₂ O) δ0.67-0.86 (2H, m), 1.26-1.59 (4H, m), 2.01 (3H, s), 2.14-2.31 (1H, m), 3.15-3.39 (2H, m), 3.71 (1H, d); m/z: (ES ⁺ ) [M+H] ⁺ =247.

Example 12: (2S,3R )-3-(aminomethyl)-6-dihydroxyboron-2-(methylamino)hexanoic acid

Intermediate 28: (2S,3R)-tert-butyl3-(azidomethyl)-2-((benzyloxycarbonyl)(methyl)amino)-6- (4,4,5,5-Tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate

(2S,3R)-tert-butyl-3-(azidomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 8, 155 mg, 0.310 mmol) was dissolved in DMF (2 mL), and the solution was cooled to 0 °C. Sodium hydride (60% wt dispersion, in oil, 15 mg, 0.37 mmol) was added, and the reaction was heated to room temperature and stirred for 15 min. Iodomethane (0.05 mL, 0.8 mmol) was added, and the reaction was stirred at room temperature for 16 h. The reaction mixture was diluted with water (15 mL) and extracted with _Et₂O (3 x 15 mL). The combined organic matter was washed with 5% lithium chloride aqueous solution (10 mL), dried over _MgSO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3R)-tert-butyl-3-(azidomethyl)-2-((benzyloxycarbonyl)(methyl)amino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil and a 55:45 mixture of rotational isomers (intermediate 28, 109 mg, 68% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.66-0.82(2H, m), 1.21(12H, s), 1.23-1.37(3H, m), 1.40(5H, s), 1.42(4H, s)1. 46-1.53 (1H, m), 2.06-2.22 (1H, m), 2.86 (3H, s), 3.37-3.55 (2H, m), 4.50 (0.55H, br d), 4.65 (0.45H, br d), 4.95-5.30 (2H, m), 7.26-7.41 (5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =534.

Example 12: (2S,3R)-3-(aminomethyl)-6-dihydroxyboron-2-(methylamino)hexanoic acid

Pd/C (10% wt, 22 mg, 0.020 mmol) and di-tert-butyl dicarbonate (115 mg, 0.530 mmol) were added to a solution of (2S,3R)-tert-butyl-3-(azidomethyl)-2-((benzyloxycarbonyl)(methyl)amino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 28, 109 mg, 0.210 mmol) in EtOAc (2 mL). A _H₂ balloon was fitted to the flask, and the suspension was stirred at room temperature for 16 h. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc. The filtrate was concentrated to dryness and then dissolved in DCM (3 mL). HBr solution (33%, in AcOH, 0.50 mL, 3.0 mmol) was added, and the reaction was stirred at room temperature for 20 min. The reaction mixture was diluted with _Et₂O (5 mL) and concentrated. This step was repeated twice. The resulting residue was dissolved in 2M HCl aqueous solution (2 mL) and Et₂O ( ₂ mL). Phenylated boric acid (51 mg, 0.42 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was purified by reversed-phase chromatography (RediSep Rf C18, 0 to 100% aqueous acetonitrile) to give a dark yellow solid. The obtained material was redissolved in MeOH (1 mL) and loaded onto a pre-equilibrated Hypersep Retain CX (2 g) ion exchange column. The resin was washed with MeOH (15 mL), followed by washing with 5% _NH₃ in MeOH solution (15 mL) to elute the product. The fraction containing the product was concentrated into a colorless residue, which was further purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 100% aqueous solution of MeCN) to give (2S,3R)-3-(aminomethyl)-6-dihydroxyboron-2-(methylamino)hexanoic acid (Example 12, 15 mg, 33%) as a white solid. ^¹H NMR (300 MHz, _D₂O ) δ 0.68–0.91 (2H, m), 1.34–1.59 (4H, m), 2.11–2.26 (1H, m), 2.60 (3H, s), 3.07 (2H, qd), 3.51 (1H, d); m/z: ( ^ES⁺ )[ _MH₂O + H] ^⁺ = 201.

Example 13: (2S,3R)-2-((S)-2-amino-3-methylbutamido)-3-(aminomethyl)-6-dihydroxyboryl hexanoic acid

Intermediate 29: (2S,3R)-tert-butyl2-((S)-2-(tert-butoxycarbonyl)-3-methylbutamido)-3- ((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Pd/C (10% wt, 180 mg, 0.16 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 23, 950 mg, 1.65 mmol) in EtOAc (12 mL). A _H₂ balloon was fitted to the flask, and the suspension was stirred at room temperature for 16 h. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc (50 mL). The filtrate was concentrated to give a pale yellow oil, which was used directly without further purification. In a separating flask, HATU (363 mg, 0.95 mmol) was added to a solution of Boc-Val-OH (210 mg, 0.95 mmol) in DMF (4 mL), and the reaction was stirred at room temperature for 10 min. The crude amine from the previous operation was divided into two equal portions (assumed to be 364 mg, 0.825 mmol), and one portion was dissolved in DMF (5 mL) and added to the second reaction flask. N,N-diisopropylethylamine (0.35 mL, 2.0 mmol) was added, and the reaction was stirred at room temperature for 2 h. The reaction mixture was diluted with EtOAc (15 mL) and washed with 1 M HCl aqueous solution (80 mL) and saturated sodium chloride aqueous solution (20 mL). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to obtain (2S,3R)-tert-butyl 2-((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless gel (intermediate 29,400 mg, 72% yield). ¹ H NMR (300MHz, DMSO-d6) δ0.55-0.69 (2H, m), 0.84 (6H, dd), 1.16 (12H, s), 1.31-1. 43(31H,m),1.83-2.07(2H,m),2.55-2.66(1H,m),2.98-3.13(1H,m),3.83(1H,br t), 4.30-4.47 (1H, m), 6.29-6.44 (1H, m), 6.72 (1H, br d), 7.83-7.94 (1H, m); m/z: (ES ^- )[M+HCOOdin=686.

Example 13: (2S,3R)-2-((S)-2-amino-3-methylbutamido)-3-(aminomethyl)-6-dihydroxyboryl hexanoic acid

HBr solution (33 wt%, in AcOH, 0.75 mL, 4.6 mmol) was added to a solution of (2S,3R)-tert-butyl-2-((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 29, 200 mg, 0.31 mmol) in DCM (4 mL), and the reaction was stirred at room temperature for 1 h. The reaction was diluted with _Et₂O (5 mL) and concentrated. This step was repeated twice. The resulting residue was dissolved in 1 M HCl aqueous solution (7 mL) and _Et₂O (5 mL). Phenylated boric acid (114 mg, 0.940 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with Et ₂ O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion exchange chromatography (PoraPak Rxn CX 20 cc column). The desired product was eluted from the column using a 5% ammonia solution of MeOH (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-2-((S)-2-amino-3-methylbutamido)-3-(aminomethyl)-6-dihydroxyboronic acid as a white solid (Example 13, 57 mg, 61% yield). ¹ H NMR (300MHz, D ₂ O)δ0.67-0.85(2H,m),0.97(6H,dd),1.16-1.56(4H,m),1.95-2.15(1H,sextet ), 2.38(1H, td), 2.76(1H, dd), 3.14(1H, dd), 3.47(1H, d), 4.41(1H, d); m/z: (ES ⁺ )[M+H] ⁺ =304.

Example 14: (2S,3R)-3-(aminomethyl)-2-((S)-2-aminopropionamido)-6-dihydroxyboronic acid

Intermediate 30: (2S,3R)-tert-butyl3-((tert-butoxycarbonylamino)methyl)-2-((S)-2-(tert-butoxy) Carbonylamino)propamido)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Pd/C (10% wt, 180 mg, 0.16 mmol) was added to a solution of (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 23, 950 mg, 1.65 mmol) in EtOAc (12 mL). A _H₂ balloon was fitted to the flask, and the suspension was stirred at room temperature for 16 h. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc (50 mL). The filtrate was concentrated to give a pale yellow oil, which was used directly without further purification. In a separating flask, HATU (363 mg, 0.95 mmol) was added to a solution of Boc-Ala-OH (180 mg, 0.95 mmol) in DMF (4 mL), and the reaction was stirred at room temperature for 10 min. The crude amine from the previous operation was divided into two equal portions (assumed to be 364 mg, 0.825 mmol), and one portion was dissolved in DMF (5 mL) and added to the second reaction flask. N,N-diisopropylethylamine (0.35 mL, 2.0 mmol) was added, and the reaction was stirred at room temperature for 16 h. The reaction mixture was diluted with EtOAc (15 mL) and washed with 1 M HCl aqueous solution (80 mL) and saturated sodium chloride aqueous solution (20 mL). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (DCM/MeOH) to obtain (2S,3R)-tert-butyl3-((tert-butoxycarbonylamino)methyl)-2-((S)-2-(tert-butoxycarbonylamino)propamido)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 30, 191 mg, 36% yield). ¹ H NMR (300MHz, CDCl ₃ )δ0.54-0.82(2H,m),0.84-1.12(2H,m),1.19(12H,s),1.29-1.38(4H,m),1.38-1.58(28H,m),2.07-2.24(1H,m),2.25- 2.44(1H,m), 3.29-3.61(1H,m), 4.05-4.19(1H,m), 4.55-4.71(1H,m), 4.86-5.14(1H,m), 5.60-6.01(1H,m), 6.66(1H,br d); m/z: (ES ⁺ )[M+H] ⁺ =614.

Example 14: (2S,3R)-3-(aminomethyl)-2-((S)-2-aminopropionamido)-6-dihydroxyboronylhexanoate HBr solution (33 wt%, in AcOH, 0.75 mL, 4.6 mmol) was added to a solution of (2S,3R)-tert-butyl-3-((tert-butoxycarbonylamino)methyl)-2-((S)-2-(tert-butoxycarbonylamino)propionamido)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 30, 191 mg, 0.310 mmol) in DCM (4 mL), and the reaction was stirred at room temperature for 1.5 h. The reaction was diluted with _Et₂O (5 mL) and concentrated. This step was repeated twice. The resulting residue was dissolved in 1 M HCl aqueous solution (7 mL) and _Et₂O (7 mL). Phenylated boric acid (114 mg, 0.940 mmol) was added, and the clear biphasic solution was stirred at room temperature for 2 h. The layers were separated, and the aqueous layer was washed with Et ₂ O (3 x 5 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion exchange chromatography (PoraPak Rxn CX 20 cc column). The desired product was eluted from the column using a 5% ammonia solution of MeOH (15 mL). The obtained material was further purified by reversed-phase chromatography (RediSep RfC18, 0 to 100% aqueous acetonitrile) to give (2S,3R)-3-(aminomethyl)-2-((S)-2-aminopropionamido)-6-dihydroxyboronic acid as a white solid (Example 14, 59 mg, 68% yield). ¹ H NMIR (300MHz, D ₂ O) δ0.67-0.87 (2H, m), 1.17-1.55 (7H, m), 2.39 (1H, tq), 2.74 (1H, dd), 3.12 (1H, dd), 3.79 (1H, q), 4.40 (1H, d); m/z: (ES ⁺ )[M+H] ⁺ =276.

Example 15: (2S,3R)-2-amino-3-(2-aminoethyl)-6-dihydroxyboronic acid dihydrochloride

Intermediate 31: (S,E)-tert-butyl4-(3-ethoxy-3-oxoprop-1-enyl)-2,2-dimethyloxazolidine-3- Formate

At 0 °C, methyl (triphenylphosphine)acetate (9.62 g, 28.8 mmol) was added to a solution of tert-butyl(R)-4-formyl-2,2-dimethyloxazolidine-3-carboxylate (6.00 g, 26.2 mmol) in toluene (220 mL). After addition, the reaction was heated to room temperature and stirred for 40 h. The reaction mixture was concentrated, and the resulting residue was diluted with _Et₂O (50 mL). The solid was removed by filtration and washed with _Et₂O (20 mL). The filtrate was concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give a mixture of (S,E)-tert-butyl-4-(3-ethoxy-3-oxoprop-1-enyl)-2,2-dimethyloxazolidine-3-carboxylate as rotational isomers (intermediate 31, 5.74 g, 77% yield). ¹ H NMR (300MHz, CDCl ₃ ) δ1.37-1.50 (9H, m), 1.51-1.57 (3H, m), 1.63 (3H, br s), 3.70-3.83(4H, m), 4.05-4.12(1H, m), 4.33-4.64(1H, m), 5.84-6.03(1H, m), 6.85(1H, br dd); m/z: (ES ⁺ )[M+H] ⁺ =286.

Intermediate 32: (S)-tert-butyl-4-((S)-1-ethoxy-1-oxohex-4-en-3-yl)-2,2-dimethyloxazole Alkyl-3-carboxylate

The three-necked flask was dried under _N2 atmosphere. Copper iodide (I) (23.4 g, 123 mmol) was added, and the solid was diluted in THF (100 mL). The suspension was cooled to 5 °C, and a solution of prop-1-en-1-yl magnesium bromide (0.5 M, in THF, 491 mL, 245 mmol) was added dropwise via an additional funnel under _N2 atmosphere. The mixture was stirred at 5 °C for 30 min, and then cooled to -78 °C. After stirring at -78 °C for 10 min, trimethylsilyl chloride (15.68 mL, 122.7 mmol) was added, followed by a solution of (S,E)-tert-butyl-4-(3-ethoxy-3-oxoprop-1-enyl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 31, 7.00 g, 24.5 mmol) in THF (20 mL). After addition, the reaction was stirred at -78°C for 30 min, then heated to -30°C to -20°C and stirred for another 30 min. At -20°C, the reaction was carefully quenched with a concentrated _NH₄OH aqueous solution: saturated _NH₄Cl aqueous solution (1:9, 200 _mL ). The crude mixture was heated to room temperature and the solids were removed by vacuum filtration. The two-phase filtrate was separated, and the aqueous phase was extracted with EtOAc (3 x 100 mL). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (S)-tert-butyl 4-((S)-1-ethoxy-1-oxohex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 32, 6.80 g, 85% yield) as a mixture of rotational isomers and E/Z olefins. ¹ H NMR (300MHz, CDCl ₃ )δ1.40-1.52(12H, m), 1.54-1.75(6H, m), 2.14-2.36(1H, m), 2.42-2.65(1H, m), 3.29-3. 55 (1H, m), 3.63 (3H, m), 3.73-4.01 (3H, m), 5.10-5.37 (1H, m), 5.46-5.70 (1H, m); m/z: (ES ⁺ )[M+H] ⁺ =328.

Intermediate 33: (S)-tert-butyl-4-((S)-1-hydroxyhex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylic acid ester

(S)-tert-butyl-4-((S)-1-ethoxy-1-oxohex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 32, 3.50 g, 10.7 mmol) was dissolved in anhydrous THF (18 mL), and the solution was cooled to 0 °C under a _nitrogen atmosphere. LAH solution (2 M, in THF, 5.34 mL, 10.7 mmol) was added dropwise to the reaction mixture, and the reaction mixture was stirred at 0 °C for 1 h. The reaction was carefully quenched at 0 °C with water (0.4 mL), 15% NaOH aqueous solution (0.4 mL), and water (1.2 mL). The resulting suspension was heated to room temperature and stirred for 10 min. _Na₂SO₄ ( ₅ g) was added, and the suspension was filtered. The solid filter cake was washed with EtOAc (50 mL). The filtrate was concentrated to dryness. The crude product was purified by silica gel chromatography (hexane/EtOAc) to give (S)-tert-butyl 4-((S)-1-hydroxyhex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 33, 3.10 g, 97% yield) as a mixture of rotational isomers and E/Z olefins. ¹ H NMR (300MHz, CDCl ₃ )δ1.43-1.52(14H, m), 1.54-1.72(6H, m), 1.73-1.88(1H, m), 2.48-3.17(1H, m), 3. 50-3.73 (2H, m), 3.75-4.01 (3H, m), 5.12-5.38 (1H, m), 5.43-5.77 (1H, m); m/z: (ES ⁺ )[M+H] ⁺ =300.

Intermediate 34: (S)-tert-butyl-2,2-dimethyl-4-((S)-1-(methylsulfonyloxy)hex-4-en-3-yl) Oxazolidine-3-carboxylate

At 0 °C, triethylamine (1.96 mL, 14.0 mmol) and methanesulfonic anhydride (2.27 g, 13.0 mmol) were added sequentially to a solution of (S)-tert-butyl-4-((S)-1-hydroxyhex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 33, 3.00 g, 10.0 mmol) in DCM (25 mL). The reaction mixture was heated to room temperature and stirred for 1 h. The crude reaction mixture was diluted with DCM (25 mL) and washed with 1 M HCl aqueous solution (10 mL) and saturated _NaHCO3 (5 mL). The organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness to give (S)-tert-butyl-2,2-dimethyl-4-((S)-1-(methanesulfonyloxy)hex- ₄ -en-3-yl)oxazolidin-3-carboxylate (intermediate 34, as a mixture of rotational isomers and E/Z olefins), which was used without further purification. ¹ H NMR (300MHz, CDCl ₃ )δ1.39-1.51(12H, m), 1.53-1.64(4H, m), 1.66-1.77(3H, m), 1.89-2.12(1H, m), 2.97(3H, s), 3.07-3.20(1H , m), 3.74-4.00 (3H, m), 4.03-4.17 (1H, m), 4.22-4.35 (1H, m), 5.05-5.27 (1H, m), 5.54-5.84 (m, 1H); m/z: (ES ⁺ )[M+H] ⁺ =378.

Intermediate 35: (S)-tert-butyl4-((S)-1-(bis(tert-butoxycarbonyl)amino)hex-4-en-3-yl)-2,2- Dimethyloxazolidine-3-carboxylate

Sodium hydride (60% wt, in oil, 427 mg, 10.68 mmol) was added to a solution of di-tert-butyl iminodicarboxylate (2.319 g, 10.68 mmol) in DMF (30 mL) at 0 °C, and the suspension was stirred at 0 °C for 20 min, then heated to room temperature and stirred for another 10 min. A solution of (S)-tert-butyl-2,2-dimethyl-4-((S)-1-(methanesulfonyloxy)hex-4-en-3-yl)oxazolidine-3-carboxylate (intermediate 34, 2.60 g, 6.89 mmol) in DMF (3 mL) was added, and the reaction was heated to 95 °C under a _N2 atmosphere for 3 h. The reaction mixture was cooled to room temperature and concentrated. The resulting residue was diluted in water (10 mL) and EtOAc (20 mL), and the layers were separated. The organic phase was dried over _Na2SO4 , _filtered , and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (S)-tert-butyl4-((S)-1-(bis(tert-butoxycarbonyl)amino)hex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 35, 2.60 g, 76% yield). ¹ H NMR (300MHz, CDCl ₃ )δ1.36-1.52(30H, m), 1.53-1.95(8H, m), 2.26-2.97(1H, m), 3.28-3.44(1H, m), 3. 48-3.66 (1H, m), 3.70-4.00 (3H, m), 5.14-5.29 (1H, m), 5.40-5.83 (1H, m); m/z: (ES ⁺ )[M+Na] ⁺ =521.

Intermediate 36: tert-butyl (tert-butoxycarbonyl) ((S)-3-((S)-1-((tert-butoxycarbonyl)amino)-2-hydroxy (Hydroxyethyl)hex-4-en-1-yl)carbamate

At room temperature, cerium(III) chloride heptahydrate (3.36 g, 9.02 mmol) and oxalic acid (0.027 g, 0.30 mmol) were added sequentially to a solution of (S)-tert-butyl-4-((S)-1-(bis(tert-butoxycarbonyl)amino)hex-4-en-3-yl)-2,2-dimethyloxazolidine-3-carboxylate (intermediate 35, 1.50 g, 3.01 mmol) in acetonitrile (30 mL). The resulting suspension was stirred at room temperature for 2 h. The suspension was filtered and the solid was washed with EtOAc. The filtrate was concentrated, diluted with EtOAc (50 mL), and washed with water (20 mL) and brine (10 mL). The organic layer was dried over _Na₂SO₄ , _filtered , and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give tert-butyl(tert-butoxycarbonyl)((S)-3-((S)-1-((tert-butoxycarbonyl)amino)-2-hydroxyethyl)hex-4-en-1-yl)carbamate (intermediate 36, 830 mg, 60% yield). ^¹H NMR (300 MHz, _CDCl₃ ) δ 1.43 (9H, s), 1.49 (18H, s), 1.56–1.85 (5H, m), 2.17–2.77 (1H, m), 3.34–3.72 (5H, m), 4.52–4.76 (1H, m), 5.13–5.35 (1H, m), 5.47–5.78 (1H, m); m/z: ( ^ES⁺ )[M+H] ^⁺ = 459.

Intermediate 37: (2S,3S)-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino) (Hexyl-4-enoic acid)

tert-Butyl(tert-Butoxycarbonyl)((S)-3-((S)-1-((tert-Butoxycarbonyl)amino)-2-hydroxyethyl)hex-4-en-1-yl)carbamate (intermediate 36, 400 mg, 0.87 mmol) was dissolved in acetone (5 mL) and cooled to -20 °C under a _nitrogen atmosphere. Jones' reagent (2.37 M, 1.14 mL, 3.05 mmol in _{aqueous H₂SO₄} solution) was slowly added, and the solution was stirred at -20 °C to -10 °C for 5 h. The reaction mixture was concentrated, and the residue was partitioned between water (10 mL) and EtOAc (10 mL). The aqueous phase was extracted with EtOAc (3 x 10 mL). The combined organics were dried over _Na₂SO₄ , _filtered , and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3S)-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)hex-4-enoic acid (intermediate 37, 200 mg, 48% yield), which was contaminated with impurities. m/z: (ES ⁺ )[M+H] ⁺ = 471.

Intermediate 38: (2S,3S)-tert-butyl-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonyl) (Hydroxyamino)hexyl-4-enoate

2-tert-butyl-1,3-diisopropylisourea (0.42 mL, 1.9 mmol) was added to a solution of (2S,3S)-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)hex-4-enoic acid (intermediate 37, 250 mg, 0.53 mmol) in DCM (5 mL), and the reaction was stirred at room temperature under a _nitrogen atmosphere for 16 h. The reaction suspension was filtered to remove insoluble solids. 2-tert-butyl-1,3-diisopropylisourea (0.05 mL, 0.2 mmol) was added to the filtrate, and the reaction was stirred at room temperature for another 48 h. The crude mixture was concentrated to dryness and purified directly by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl 3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)hex-4-enoate as a viscous oil (intermediate 38, 120 mg, 43% yield). ¹ H NMR (300MHz, CDCl ₃ )δ1.33-1.57(37H,m), 1.60-1.68(3H,m), 1.71-1.90(1H,m), 2.45-3.06(1H,m), 3.37-3.6 6(2H, m), 4.20-4.28(1H, m), 4.90-5.08(1H, m), 5.18(1H, td), 5.44-5.87(1H, m); m/z: (ES ⁺ )[M+Na] ⁺ =551.

Intermediate 39: (2S,3R)-tert-butyl-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonyl) (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (15 mg, 0.022 mmol) and bis(diphenylphosphine)methane (17 mg, 0.046 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2) . The solid was dissolved in DCM (2.6 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.21 mL, 1.4 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)hex-4-enoate (intermediate 38, 300 mg, 0.57 mmol) was added to the reaction as a solution in DCM (2 mL), and the reaction was stirred at room temperature for 24 h. The reaction mixture was concentrated to dryness and purified directly by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl 3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 39, 100 mg, 27% yield). ¹ H NMR (300MHz, CDCl ₃ ) δ0.73 (2H, t), 1.22 (12H, s), 1.43 (12H, s), 1.46-1.74 (30H, m), 1.80-1.90 (1H, br d), 3.42-3.77 (2H, m), 4.28 (1H, brdd), 5.03 (1H, br d); m/z: (ES ⁺ )[M+Na] ⁺ =679.

Example 15: (2S,3R)-2-amino-3-(2-aminoethyl)-6-dihydroxyboronic acid dihydrochloride

(2S,3R)-tert-butyl-3-(2-(bis(tert-butoxycarbonyl)amino)ethyl)-2-(tert-butoxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 39, 230 mg, 0.35 mmol)) was dissolved in HCl (4 M, in dioxane, 1.75 mL, 7.01 mmol), and the reaction was stirred at room temperature under a _nitrogen atmosphere for 30 min. The reaction was heated to 60 °C and stirred for 1 h. The reaction was cooled to room temperature and diluted with 1 M HCl aqueous solution (1 mL). Phenylboronic acid (214 mg, 1.75 mmol) was added, and the reaction was heated to 60 °C for 1 h. The reaction mixture was cooled to room temperature, and volatiles were removed under vacuum. The crude solution was diluted with water (5 mL) and washed with EtOAc (4 x 3 mL). The aqueous phase was freeze-dried to give (2S,3R)-2-amino-3-(2-aminoethyl)-6-dihydroxyboronic hexanoic acid dihydrochloride as a dry thin film (Example 15, 80 mg, 78% yield). ^¹H NMR (300 MHz, _D₂O ) δ 0.81 (2H, br t), 1.35–1.55 (4H, m), 1.72–1.91 (2H, m), 2.06–2.30 (1H, m), 3.05–3.23 (2H, m), 4.07 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 219.

Example 16: (2S,3S)-2-amino-6-dihydroxyboron-3-carbamoylhexanoic acid

Intermediate 40: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-carbamoylhex-5-enoate

HATU (311 mg, 0.818 mmol), ammonium chloride (159 mg, 2.97 mmol), and N,N-diisopropylethylamine (0.78 mL, 4.5 mmol) were added to a solution of 2-((S)-1-(benzyloxycarbonylamino)-2-tert-butoxy-2-oxoethyl)pent-4-enoic acid (intermediate 3, 270 mg, 0.74 mmol) in DMF (3 mL), and the reaction was stirred at room temperature for 15 _h . The mixture was diluted with DCM and a saturated aqueous solution of ammonium chloride. The layers were separated, and the aqueous layer was extracted with DCM. The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give pure diastereomeric (2S,3S)-tert-butyl 2-(benzyloxycarbonylamino)-3-carbamoyl hex-5-enoate (intermediate 40, 148 mg, 55% yield) and (2S,3R)-tert-butyl 2-(benzyloxycarbonylamino)-3-carbamoyl hex-5-enoate (86 mg, 32% yield). The stereochemistry of the major diastereomeric derivative was specified by analogy with previous analogs. ¹ H NMR (500MHz, CDCl ₃ )δ1.39(9H, s), 2.26-2.47(2H, m), 2.78-3.00(1H, m), 4.19-4.43(1H, m), 5.01-5.16(4H, m), 5.71- 5.81 (1H, m), 5.82-5.87 (1H, m), 5.96-6.05 (1H, m), 6.13-6.21 (1H, m), 7.25-7.37 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =363.

Intermediate 41: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-carbamoyl-6-(4,4,5,5-tetra-) Methyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (15 mg, 0.022 mmol) and bis(diphenylphosphine)ethane (18 mg, 0.045 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2) . The solid was dissolved in DCM (1.5 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (67 μL, 0.46 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-carbamoylhex-5-enoate (intermediate 40, 84 mg, 0.23 mmol) was added to the reaction as a solution in DCM (1 mL), and the reaction was stirred at room temperature for 15 h. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-carbamoyl-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 41,73 mg, 64% yield). ¹ H NMR (400MHz, CDCl ₃ )δ0.72-0.82(2H,m),1.20(12H,s),1.34-1.41(9H,m),1.43-1.52(2H,m),1.53-1.62(1H,m),1.62-1.72(1H,m),2.68-2.93(1H , m), 4.19-4.40 (1H, m), 5.01-5.09 (1H, m), 5.09-5.16 (1H, m), 5.67-5.94 (2H, m), 6.04-6.25 (1H, m), 7.24-7.35 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =491.

Example 16: (2S,3S)-2-amino-6-dihydroxyboron-3-carbamoylhexanoic acid

HBr solution (33 wt%, in AcOH, 0.5 mL, 2.8 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-carbamoyl-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 41, 73 mg, 0.15 mmol) in DCM (2 mL), and the reaction was stirred at room temperature for 1 h. The reaction was concentrated, and the resulting residue was diluted in _Et₂O (2 mL) and 2M HCl aqueous solution (2 mL). Phenylated boric acid (36 mg, 0.30 mmol) was added, and the clear biphasic solution was stirred at room temperature for 15 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion exchange chromatography (PoraPak Rxn CX 20cc column). The desired product was eluted from the column using 15 mL of 5% ammonia in MeOH solution to give (2S,3S)-2-amino-6-dihydroxyboron-3-carbamoylhexanoic acid as a white solid (Example 16, 31 mg, 96% yield). ^¹H NMR (500 MHz, _D₂O ) δ 0.79 (2H, td), 1.44 (2H, quin), 1.53–1.61 (1H, m), 1.64–1.73 (1H, m), 2.87–3.00 (1H, m), 3.77 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 219.

Example 17: (2S,3S)-2-amino-6-dihydroxyboron-3-(methylcarbamoyl)hexanoic acid

Intermediate 42: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)hex-5-enoic acid ester

HATU (266 mg, 0.699 mmol), methylamine hydrochloride (172 mg, 2.54 mmol), and N,N-diisopropylethylamine (0.67 mL, 3.8 mmol) were added to a solution of 2-((S)-1-(benzyloxycarbonylamino)-2-tert-butoxy-2-oxoethyl)pent-4-enoic acid (intermediate 3, 231 mg, 0.64 mmol) in DMF (3 mL), and the reaction was stirred at room temperature for 15 _h . The mixture was diluted with DCM and a saturated aqueous solution of ammonium chloride. The layers were separated, and the aqueous layer was extracted with DCM. The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give pure diastereomeric (2S,3S)-tert-butyl 2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)hex-5-enoate (intermediate 42, 133 mg, 56% yield) and (2S,3R)-tert-butyl 2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)hex-5-enoate (77 mg, 32% yield). The stereochemistry of the major diastereomeric derivative was specified by analogy with previous analogs. ¹ H NMR (500MHz, CDCl ₃ )δ1.37(9H, s), 2.24-2.45(2H, m), 2.71(3H, d), 2.81(1H, td), 4.19-4.41(1H, m), 4.96-5.18 (4H, m), 5.66-5.77 (1H, m), 5.77-5.84 (1H, m), 6.09-6.35 (1H, m), 7.24-7.36 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =377.

Intermediate 43: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)-6-(4,4, 5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (8.1 mg, 0.012 mmol) and bis(diphenylphosphino)ethane (9.7 mg, 0.024 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2) . The solid was dissolved in DCM (1 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (59 μL, 0.40 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)hex-5-enoate (intermediate 42.76 mg, 0.20 mmol) was added to the reaction as a solution in DCM (1.5 mL), and the reaction was stirred at room temperature for 15 h. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 43, 70 mg, 69% yield). ¹ H NMR (500MHz, CDCl ₃ )δ0.64-0.87(2H,m),1.20(13H,s),1.31-1.45(10H,m),1.49-1.60(1H,m),1.63-1.72(1H,m),2.60-2.77(4H,m),4.30(1H,br dd), 5.02-5.09(1H, m), 5.09-5.16(1H, m), 5.75-5.91(1H, m), 6.28(1H, br d), 7.24-7.35(5H, m); m/z: (ES ⁺ )[M+H] ⁺ =505.

Example 17: (2S,3S)-2-amino-6-dihydroxyboron-3-(methylcarbamoyl)hexanoic acid

HBr solution (33 wt%, in AcOH, 0.5 mL, 2.8 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(methylcarbamoyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 43, 70 mg, 0.14 mmol) in DCM (2 mL), and the reaction was stirred at room temperature for 1 h. The reaction was concentrated, and the resulting residue was diluted in _Et₂O (2 mL) and 2 M HCl aqueous solution (2 mL). Phenylated boric acid (34 mg, 0.28 mmol) was added, and the clear biphasic solution was stirred at room temperature for 15 h. The layers were separated, and the aqueous layer was washed with _Et₂O (3 x 10 mL) and lyophilized. The resulting solid was dissolved in MeOH (1 mL) and purified by ion exchange chromatography (PoraPak Rxn CX 20 cc column). The desired product was eluted from the column using 15 mL of 5% ammonia in MeOH solution to give (2S,3S)-2-amino-6-dihydroxyboron-3-(methylcarbamoyl)hexanoic acid as a white solid (Example 17, 30 mg, 93% yield). ^¹H NMR (500 MHz, _D₂O ) δ 0.71–0.85 (2H, m), 1.31–1.45 (2H, m), 1.51–1.60 (1H, m), 1.62–1.73 (1H, m), 2.67 (3H, s), 2.89 (1H, dt), 3.80 (1H, d); m/z: ( ^ES⁺ )[M+H] ^⁺ = 233.

Example 18: (2S,3S)-2-amino-3-(aminomethyl)-6-dihydroxyboronic acid dihydrochloride

Intermediate 44: (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hexyl- 5-Olefin ester

At 0 °C, triethylamine (1.70 mL, 12.2 mmol) and methanesulfonyl chloride (0.60 mL, 7.7 mmol) were added to a solution of (2S,3R)-tert-butyl 2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 5, 1.00 g, 2.86 mmol) in DCM (20 mL). The reaction was heated to room temperature and stirred for 90 min. The crude mixture was diluted with DCM (10 mL) and washed successively with saturated sodium bicarbonate aqueous solution, water, and brine (25 mL each). The organic layer was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3R)-tert-butyl 2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hex-5-enoate (intermediate 44, 1.17 g, 96% yield) as a pale yellow oil. ¹ H NMR (300MHz, CDCl ₃ ) δ1.46 (9H, s), 1.94-2.11 (1H, m), 2.18-2.32 (1H, m), 2.34-2.53 (1H, m), 2.97 (3H, s), 4.12-4.24 (2H, m), 4.45 (1H, br dd), 5.00-5.18(4H, m), 5.42(1H, br d), 5.63-5.89(1H, m), 7.25-7.37(5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =445.

Intermediate 45: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2- methyl 5-hexanoate

Under a _nitrogen atmosphere, potassium phthalimide (0.558 g, 3.01 mmol) and potassium iodide (0.227 g, 1.37 mmol) were added to an oven-dried flask. (2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-((methanesulfonyloxy)methyl)hex-5-enoate (intermediate 44, 1.17 g, 2.74 mmol) was added as a solution in DMF (15 mL), and the reaction was heated to 95 °C for 3 h. The reaction mixture was cooled to room temperature and diluted with water (30 mL). The layers were separated, and the aqueous layer was extracted with _Et₂O (3 x 20 mL). The combined organic matter was dried over _MgSO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtAOc) to obtain (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2-yl)methyl)hex-5-enoate as a colorless oil (intermediate 45, 0.725 g, 55% yield). ¹ HNMR (300MHz, CDCl ₃ ) δ1.20 (9H, s), 2.04-2.26 (2H, m), 2.69 (1H, pentet), 3.61 (2H, d), 4.47 (1H, br d), 4.98-5.22(4H, m), 5.75-5.94(1H, m), 5.99(1H, br d), 7.25-7.42(5H, m), 7.63-7.72(2H, m), 7.77-7.87(2H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =496.

Intermediate 46: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2- (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (31 mg, 0.046 mmol) and bis(diphenylphosphine)methane (35 mg, 0.090 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (5 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.50 mL, 3.5 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2-yl)methyl)hex-5-enoate (intermediate 45,725 mg, 1.52 mmol) was added to the reaction as a solution in DCM (4 mL), and the reaction was stirred at room temperature for 15 h. The reaction mixture was cooled to 0°C and quenched with MeOH (2 mL) and water (10 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2-yl)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a glassy, colorless residue (intermediate 46,612 mg, 67% yield). ¹ H NMR (300MHz, CDCl ₃ ) δ0.79 (2H, br t), 1.19 (12H, s), 1.21 (9H, s), 1.25-1.54 (3H, m), 1.59-1.77 (1H, m), 2.51-2.66 (1H, m), 3.49-3.67 (2H, m), 4.44 (1H, br d), 5.11 (2H, s), 5.96 (1H, brd), 7.26-7.41 (5H, m), 7.61-7.72 (2H, m), 7.75-7.85 (2H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =624.

Example 18: (2S,3S)-2-amino-3-(aminomethyl)-6-dihydroxyboronic acid dihydrochloride

(2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((1,3-dioxoisoindoline-2-yl)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 46, 315 mg, 0.520 mmol) was dissolved in 6 M HCl aqueous solution (5 mL), and the solution was heated to 100 °C for 16 h. The reaction was cooled to room temperature, diluted with water (10 mL), and washed with ether (3 x 10 mL). The aqueous layer was lyophilized and purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 100% MeCN aqueous solution) to give (2S,3S)-2-amino-3-(aminomethyl)-6-dihydroxyboronylhexanoate dihydrochloride as a yellow solid (Example 18, 94 mg, 65% yield). ¹ H NMR (300MHz, D ₂ O) δ 0.73-0.91 (2H, m), 1.34-1.64 (4H, m), 2.29-2.45 (1H, m), 3.27 (2H, qd), 4.16 (1H, d); m/z: (ES ⁺ )[MH ₂ O+H] ⁺ =187.

Example 19: (2S,3S)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyboryl hexanoic acid

Intermediate 47: (2S,3S)-tert-butyl2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(tri-) Methylsilyl)ethylsulfonamide)methyl)hexyl-5-enoate

(2S,3R)-tert-butyl-2-(benzyloxycarbonylamino)-3-(hydroxymethyl)hex-5-enoate (intermediate 5,747 mg, 2.14 mmol) and tert-butyl((2-(trimethylsilyl)ethyl)sulfonyl)carbamate (602 mg, 2.14 mmol) were dissolved in THF (10 mL) and cooled to 0 °C. Triphenylphosphine (842 mg, 3.21 mmol) and DIAD (0.85 mL, 4.4 mmol) were added, and the reaction was stirred for 16 h while slowly heated to room temperature. The reaction was quenched with saturated sodium bicarbonate aqueous solution (20 mL), and the layers were separated. The aqueous layer was extracted with EtOAc (2 x 15 mL). The combined organic layers were dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3S)-tert-butyl2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(trimethylsilyl)ethylsulfonamide)methyl)hex-5-enoate (intermediate 47,860 mg, 66% yield). ¹ H NMR (500MHz, CDCl ₃ )0.04(9H,s),0.91-1.01(2H,m),1.46(9H,s),1.50(9H,s),2.04-2.13(2H , m), 2.41-2.65 (1H, m), 3.33-3.47 (2H, m), 3.58-3.81 (2H, m), 4.40 (1H, br d), 4.96-5.19 (4H, m), 5.66 (1H, br d), 5.72-5.96 (1H, m), 7.25-7.41 (5H, m); m/z: (ES ⁺ )[M+NH ₄ ] ⁺ =630.

Intermediate 48: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl) Hex-5-enoate

TBAF solution (1M, in THF, 6.0 mL, 6.0 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((N-(tert-butoxycarbonyl)-2-(trimethylsilyl)ethylsulfonamide)methyl)hex-5-enoate (intermediate 47, 1.23 g, 2.01 mmol) in THF (6 mL), and the reaction was stirred at room temperature for 30 min. The reaction mixture was diluted with _Et₂O (30 mL) and washed successively with water (3 x 15 mL). The organic layer was dried over _MgSO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)hex-5-enoate (intermediate 48, 834 mg, 93% yield) as a pale yellow oil. ¹ HNMR (500MHz, CDCl ₃ )δ1.41(9H,s),1.45(9H,s),1.90-1.99(1H,m),2.06-2.16(1H,m),2.17-2.30(1H,m),2.92-3.14(1H,m),3.14-3.27(1H,m),4.36(1H,br dd), 4.46-4.69 (1H, m), 5.03-5.15 (4H, m), 5.70-5.92 (2H, m), 7.26-7.39 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =449.

Intermediate 49: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)- 6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

Bis(1,5-cyclooctadiene)diiridium(I) chloride (48 mg, 0.071 mmol) and bis(diphenylphosphine)methane (55 mg, 0.14 mmol) were added to an oven-dried round-bottom flask. The flask was sealed and purged with nitrogen ( _N2 ). The solid was dissolved in DCM (7 mL), and 4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane (0.76 mL, 5.2 mmol) was slowly added to the solution. The reaction was stirred at room temperature for 10 min. (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)hex-5-enoate (intermediate 48, 1.071 g, 2.39 mmol) was added to the reaction as a solution in DCM (6 mL), and the reaction was stirred at room temperature for 15 h. The reaction mixture was cooled to 0 °C and quenched with MeOH (2 mL) and water (15 mL). The layers were separated and the aqueous layer was extracted with DCM (2 x 10 mL). The combined organic matter was dried over _MgSO4 , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate, a pale yellow gel (intermediate 49 g, 1.01 g, 73% yield). ¹ H NMR (500MHz, CDCl ₃ ) δ0.75 (2H, br t), 1.20 (12H, s), 1.30-1.38 (2H, m), 1.40 (9H, s), 1.43 (9H, s), 1.46-1.51 (2H, m), 2.09 (1H, br s), 2.98-3.12(1H, m), 3.12-3.25(1H, m), 4.30(1H, br dd), 4.55-4.79(1H, m), 5.01-5.18(2H, m), 5.77(1H, br d), 7.25-7.38(5H, m); m/z: (ES ⁺ )[M+H] ⁺ =577.

Intermediate 50: (2S,3S)-tert-butyl3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-((4,4,5,5-tetramethylamino) Methyl-1,3,2-dioxaneborane-2-yl)hexanoate

At 0 °C, HCl solution (4 M, in dioxane, 3.35 mL, 13.4 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 49,773 mg, 1.34 mmol) in dioxane (3.5 mL). The reaction was stirred for 2 h while being slowly heated to room temperature. The solution was concentrated to dryness to give (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50,639 mg, 100% yield) as a grayish-white solid, which was used without further purification. m/z: (ES ⁺ )[M+H] ⁺ =476.

Intermediate 51: (2S3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

HATU (385 mg, 1.01 mmol) was added to a solution of Boc-Val-OH (220 mg, 1.01 mmol) in DMF (4 mL), and the reaction was stirred at room temperature for 10 min. Then, (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 438 mg, 0.919 mmol) was added to the reaction as a solution in DMF (6 mL). N,N-diisopropylethylamine (0.80 mL, 4.6 mmol) was added, and the reaction was stirred at room temperature for 3 _h . The reaction mixture was diluted with saturated _NH₄Cl aqueous solution and DCM, and the layers were separated. The aqueous layer was extracted with DCM (3 x 20 mL). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 51,450 mg, 72% yield), which was a white foam. ¹ H NMR (500MHz, CDCl ₃ ) δ0.72 (2H, br t), 0.80-0.97(6H, m), 1.13-1.35(13H, m), 1.37-1.63(21H, m), 1.95(1H, brs), 2.07-2.17(1H, m), 3.07-3.31(1H, m), 3.34-3.54( 1H, m), 3.80-4.00 (1H, m), 4.14-4.28 (1H, m), 5.00-5.23 (3H, m), 5.50-5.78 (1H, m), 6.28-6.70 (1H, m), 7.25-7.45 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ ＝676.

Example 19: (2S,3S)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyboryl hexanoic acid

Pd/C (10 wt%, 71 mg, 0.070 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3-methylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 51,450 mg, 0.67 mmol) in EtOAc (10 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated to dryness, and the resulting residue was dissolved in HCl (4 M, in dioxane, 10.0 mL, 40.0 mmol). The reaction was heated to 50 °C and stirred for 1.5 h. The reaction was cooled to room temperature and concentrated. The resulting residue was dissolved in 1M HCl aqueous solution (15 mL) and _Et₂O (15 mL). Phenylated boric acid (155 mg, 1.27 mmol) was added, and the reaction was stirred at room temperature for 4 h. The reaction mixture was diluted with water and washed with _Et₂O . The aqueous layer was lyophilized and purified by ion-exchange chromatography (PoraPakRxn CX 20 cc column). The desired product was eluted from the column with 2.5 M ammonia/methanol to give (2S,3S)-2-amino-3-(((S)-2-amino-3-methylbutamido)methyl)-6-dihydroxyboronic acid (Example 19, 147 mg, 76% yield) as a white solid. ¹ H NMR (500MHz, D ₂ O) δ 0.70-0.85 (2H, m), 0.91-1.01 (6H, m), 1.29-1.56 (4H, m), 1.94-2.05 (1H, m), 2.17-2.31 (1H, m), 3.26-3.44 (3H, m), 3.70 (1H, d); m/z: (ES ⁺ )[M+H] ⁺ =304.

Example 20: (2S,3S)-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid

Intermediate 52: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

HATU (561 mg, 1.48 mmol) was added to a solution of Boc-Ala-OH (279 mg, 1.48 mmol) in DMF (4 mL), and the reaction was stirred at room temperature for 10 min. Then, (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 639 mg, 1.34 mmol) in DMF (6 mL) was added to the reaction. N,N-diisopropylethylamine (1.17 mL, 6.71 mmol) was added, and the reaction was stirred at room temperature for 3 h. The reaction mixture was diluted with saturated _NH₄Cl aqueous solution and DCM, and the layers were separated. The aqueous layer was extracted with DCM (3 x 30 _mL ). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)propamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a white solid (intermediate 52,662 mg, 76% yield). ¹ H NMR (500MHz, CDCl ₃ ) δ0.65-0.78 (2H, m), 1.19 (12H, s), 1.32 (3H, br d), 1.37-1.55(22H, m), 1.95-2.07(1H, m), 3.10-3.27(1H, m), 3.30-3.50(1H, m), 3.87-4.45(2H, m), 5.08(2H, br s), 5.13-5.23(1H, m), 5.76(1H, br s), 6.52-6.80(1H, m), 7.25-7.44(5H, m); m/z: (ES ⁺ )[M+H] ⁺ =648.

Example 20: (2S,3S)-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid

Pd/C (10 wt%, 110 mg, 0.10 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)propamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 52,662 mg, 1.02 mmol) in _Et₂O (10 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated to dryness, and the resulting residue was dissolved in HCl (4 M, in dioxane, 10.0 mL, 40.0 mmol), and the reaction was stirred at room temperature for 3.5 h. The reaction mixture was concentrated, and the resulting solid was ground together with _Et₂O . The solid was dissolved in 1M HCl aqueous solution (15 mL) and _Et₂O (15 mL). Phenylated boric acid (245 mg, 2.01 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with water and washed with _Et₂O . The aqueous layer was lyophilized and purified by ion exchange chromatography (Silicycle SPE-R51230B-20X column). The desired product was eluted from the column with 2.5 M ammonia/methanol to give (2S,3S)-2-amino-3-(((S)-2-aminopropamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 20, 250 mg, 91% yield). ¹ H NMR (500MHz, D ₂ O) δ0.68-0.79 (2H, m), 1.26 (3H, br d), 1.29-1.36 (2H, m), 1.37-1.49 (2H, m), 2.10-2.27 (1H, m), 3.16-3.37 (2H, m), 3.50-3.64 (2H, m); m/z: (ES ⁺ )[M+H] ⁺ =276.

Example 21: (2S,3S)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronic acid

Intermediate 53: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino) (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

N,N-diisopropylethylamine (0.49 mL, 2.8 mmol) was added to a suspension of HATU (220 mg, 0.58 mmol) and Boc-Abu-OH (230 mg, 1.13 mmol) in DCM (3 mL), and the reaction was stirred at room temperature for 10 min. DMF (1 mL) was added to the suspension, and the reaction was stirred at room temperature for another 5 min. A solution of (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 238 mg, 0.499 mmol) in DCM (2 mL) was added, and the reaction was stirred at room temperature overnight. The reaction mixture was diluted with water and DCM, and the layers were separated. The aqueous layer was extracted with DCM (2 x 20 mL). The combined organic matter was washed with saturated sodium chloride, _dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)butamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 53, 110 mg, 29% yield). ¹ H NMR (500MHz, CDCl ₃ ) δ0.73 (2H, br s), 0.91 (3H, br s), 1.21 (13H, br s), 1.30-1.37 (1H, m), 1.39-1.43 (9H, m), 1.45 (9H, br s), 1.49-1.65(2H, m), 1.86(1H, br s), 2.00(1H, br s), 2.14-2.69(1H, m), 3.20(1H, br s), 3.31-3.61(1H, m), 3.99(1H, br s), 4.13-4.34(1H, m), 5.09(3H, br s), 5.66-5.88 (1H, m), 6.46-6.72 (1H, m), 7.28-7.39 (5H, m).

Example 21: (2S,3S)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronic acid

Pd/C (10 wt%, 43 mg, 0.040 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)butamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 53, 107 mg, 0.162 mmol) in ethyl acetate (5 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated, and the resulting residue was dissolved in DCM (1 mL) and trifluoroacetic acid (3 mL), and the reaction was stirred overnight at room temperature. The reaction was concentrated, and the residue was dissolved in 1 M HCl aqueous solution (2 mL) and Et₂O ( ₂ mL). Phenylated boric acid (38 mg, 0.31 mmol) was added, and the reaction was stirred at room temperature for 3 h. The reaction mixture was diluted with water and washed with Et ₂ O. The aqueous layer was lyophilized and purified by ion-exchange chromatography (PoraPak Rxn CX 20cc column). The desired product was eluted from the column with a methanol solution of 5% ammonia to give (2S,3S)-2-amino-3-(((S)-2-aminobutamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 21, 40 mg, 89% yield). ¹ H NMR (500MHz, D ₂ O)δ0.74(2H, td), 0.85(3H, brt), 1.27-1.36(2H, m), 1.37-1.47(2H, m), 1.56-1.7 1(2H, m), 2.11-2.20(1H, m), 3.20-3.35(2H, m), 3.39(1H, t), 3.60(1H, d); m/z: (ES ⁺ )[M+H] ⁺ =290.

Example 22: (2S,3S)-2-amino-3-(((2S,3S)-2-amino-3-methylpentamido)methyl)-6-dihydroxy Boronylhexanoic acid

Intermediate 54: (2S,3S)-tert-butyl2-(benzyloxycarbonylamino)-3-(((2S,3S)-2-(tert-butoxycarbonyl) (amino)-3-methylpentamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

N,N-diisopropylethylamine (0.84 mL, 4.8 mmol) was added to a suspension of HATU (365 mg, 0.960 mmol) and Boc-Ile-OH (462 mg, 2.00 mmol) in DCM (3 mL) and DMF (3 mL), and the reaction was stirred at room temperature for 10 min. A solution of (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 336 mg, 0.705 mmol) in DCM (3 mL) was added, and the reaction was stirred at room temperature overnight. The reaction mixture was diluted with water and DCM, and the layers were separated. The aqueous layer was extracted with DCM (2 x 20 _mL ). The combined organics were washed with saturated sodium bicarbonate, dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((2S,3S)-2-(tert-butoxycarbonylamino)-3-methylpentamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 54,260 mg, 47% yield). ¹ H NMR (500MHz, CDCl ₃ ) δ0.73 (2H, br t), 0.83-0.97 (6H, m), 1.08 (1H, br s), 1.21 (13H, br s), 1.29-1.63(22H, m), 1.82-1.92(1H, m), 1.92-2.04(1H, m), 3.18(1H, br s), 3.43(1H, br d), 3.96(1H, br s), 4.21(1H, br d), 5.09(3H, br s), 5.58-5.80 (1H, m), 6.40-6.69 (1H, m), 7.29-7.40 (5H, m).

Example 22: (2S,3S)-2-amino-3-(((2S,3S)-2-amino-3-methylpentamido)methyl)-6-dihydroxy Boronylhexanoic acid

Pd/C (10 wt%, 99 mg, 0.093 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((2S,3S)-2-(tert-butoxycarbonylamino)-3-methylpentamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 54,256 mg, 0.371 mmol) in ethyl acetate (8 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated, and the resulting residue was dissolved in DCM (2 mL) and trifluoroacetic acid (6 mL), and the reaction was stirred at room temperature for 3 h. The reaction was concentrated, and the residue was dissolved in 1 M HCl aqueous solution (2 mL) and _Et₂O (5 mL). Phenylated boric acid (82 mg, 0.67 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with water and washed with Et ₂ O. The aqueous layer was lyophilized and purified by ion-exchange chromatography (PoraPak Rxn CX 20cc column). The desired product was eluted from the column with a methanol solution of 5% ammonia to give (2S,3S)-2-amino-3-(((2S,3S)-2-amino-3-methylpentamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 22, 93 mg, 87% yield). ¹ H NMR (500MHz, D ₂ O) δ0.68-0.78 (2H, m), 0.80-0.91 (6H, m), 1.07-1.18 (1H, m), 1.27-1.48 (5H, m), 1.69 (1H, brd), 2.14 (1H, br d), 3.21-3.36 (3H, m), 3.62 (1H, br d); m/z: (ES ⁺ )[M+H] ⁺ =318.

Example 23: (2S,3S)-2-amino-3-(((S)-2-amino-3,3-dimethylbutamido)methyl)-6-dihydroxy Boronylhexanoic acid

Intermediate 55: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((((S)-2-(tert-butoxycarbonylamino) (4,4,5,5-Tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoic acid ester

N,N-diisopropylethylamine (1.08 mL, 6.20 mmol) was added to a suspension of HATU (472 mg, 1.24 mmol) and Boc-Tle-OH (550 mg, 2.4 mmol) in DCM (3 mL) and DMF (3 mL), and the reaction was stirred at room temperature for 10 min. A solution of (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 434 mg, 0.911 mmol) in DCM (4.5 mL) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with water and DCM, and the layers were separated. The aqueous layer was extracted with DCM (2 x 20 _mL ). The combined organics were washed with saturated sodium bicarbonate, dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to obtain (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3,3-dimethylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a colorless oil (intermediate 55,560 mg, 79% yield). ^¹H NMR (500 MHz, _CDCl₃ ) δ 0.75 (2H, br⁻) t), 0.95-1.05 (9H, m), 1.18-1.25 (13H, m), 1.32-1.40 (1H, m), 1.42-1.45 (9H, m), 1 .46-1.51(9H,m), 1.52-1.62(1H,m), 1.64-1.73(1H,m), 1.88-2.04(1H,m), 3.08-3. 27(1H,m),3.39-3.56(1H,m),3.74-3.90(1H,m),4.18-4.30(1H,m),5.05-5.17(2H , m), 5.31 (1H, s), 5.47-5.80 (1H, m), 6.14-6.44 (1H, m), 7.30-7.40 (5H, m); m/z: (ES ⁺ )[M+H] ⁺ =690.

Example 23: (2S,3S)-2-amino-3-(((S)-2-amino-3,3-dimethylbutamido)methyl)-6-dihydroxy Boronylhexanoic acid

Pd/C (10 wt%, 138 mg, 0.130 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-(((S)-2-(tert-butoxycarbonylamino)-3,3-dimethylbutamido)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 55, 359 mg, 0.521 mmol) in ethyl acetate (12 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated, and the resulting residue was dissolved in DCM (3 mL) and trifluoroacetic acid (9 mL), and the reaction was stirred at room temperature for 3 h. The reaction was concentrated, and the residue was dissolved in 1 M HCl aqueous solution (3 mL) and _Et₂O (5 mL). Phenylated boric acid (127 mg, 1.04 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with water and washed with Et ₂ O. The aqueous layer was lyophilized and purified by ion-exchange chromatography (PoraPak Rxn CX 20cc column). The desired product was eluted from the column with a methanol solution of 5% ammonia. The obtained material was further purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 10% aqueous acetonitrile) to give (2S,3S)-2-amino-3-(((S)-2-amino-3,3-dimethylbutamido)methyl)-6-dihydroxyboronic acid (Example 23, 96 mg, 58% yield) as a white solid. ¹ H NMR (500MHz, D ₂ O w/TFA) δ0.52-0.73 (2H, m), 0.90 (9H, s), 1.17-1.41 (4H, m), 2.11-2.23 (1H, m), 3.21-3.34 (2H, m), 3.49-3.55 (1H, m), 3.91-4.00 (1H, m); m/z: (ES ⁺ )[M+H] ⁺ =318.

Example 24: (2S,3S)-2-amino-3-((2-aminoacetamido)methyl)-6-dihydroxyboronic acid

Intermediate 56: (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((2-(tert-butoxycarbonylamino)ethyl) (Amide)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate

N,N-diisopropylethylamine (0.92 mL, 5.3 mmol) was added to a suspension of HATU (434 mg, 1.14 mmol) and Boc-Gly-OH (400 mg, 2.28 mmol) in DCM (3 mL) and DMF (3 mL), and the reaction was stirred at room temperature for 10 min. A solution of (2S,3S)-tert-butyl-3-(aminomethyl)-2-(benzyloxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 50, 369 mg, 0.775 mmol) in DCM (3 mL) was added, and the reaction was stirred at room temperature overnight. The reaction mixture was diluted with water and DCM, and the layers were separated. The aqueous layer was extracted with DCM (2 x 20 _mL ). The combined organics were washed with saturated sodium chloride, dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((2-(tert-butoxycarbonylamino)acetamyl)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 56,259 mg, 47% yield). ¹ H NMR (500MHz, CDCl ₃ ) δ0.72 (2H, br s), 1.19 (13H, br s), 1.28-1.36 (1H, m), 1.36-1.45 (18H, m), 1.45-1.56 (2H, m), 2.03-2.13 (1H, m), 3.12 (1H, br s), 3.41 (1H, br d), 3.61-3.89(2H, m), 4.16-4.38(1H, m), 5.07(2H, br s), 5.30-5.43(1H, m), 5.95(1H, br s), 6.73(1H, br s), 7.22-7.36(5H, m).

Example 24: (2S,3S)-2-amino-3-((2-aminoacetamido)methyl)-6-dihydroxyboronic acid

Pd/C (10 wt%, 107 mg, 0.101 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((2-(tert-butoxycarbonylamino)acetamyl)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 56, 256 mg, 0.404 mmol) in ethyl acetate (8 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc and methanol. The filtrate was concentrated, and the resulting residue was dissolved in DCM (2 mL) and trifluoroacetic acid (6 mL), and the reaction was stirred at room temperature for 3 h. The reaction was concentrated, and the residue was dissolved in 1 M HCl aqueous solution (3 mL) and _Et₂O (5 mL). Phenylated boric acid (98 mg, 0.80 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with water and washed with Et ₂ O. The aqueous layer was lyophilized and purified by ion-exchange chromatography (PoraPak Rxn CX 20cc column). The desired product was eluted from the column with a methanol solution of 5% ammonia. The obtained material was further purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 5% aqueous acetonitrile) to give (2S,3S)-2-amino-3-((2-aminoacetamido)methyl)-6-dihydroxyboronic acid as a white solid (Example 24, 20 mg, 19% yield). ¹ H NMR (500MHz, D ₂ O w/TFA) δ0.53-0.74 (2H, m), 1.16-1.45 (4H, m), 2.17-2.31 (1H, m), 3.16-3.36 (2H, m), 3.57-3.71 (2H, m), 3.96 (1H, d); m/z: (ES ⁺ )[M+H] ⁺ =262.

Example 25: (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-aminopropionyl]amino]-6-dihydroxyboryl-hexyl acid

Intermediate 57: tert-butyl(2S,3S)-2-amino-3-[(tert-butoxycarbonylamino)methyl]-6-(4,4,5,5- Tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate

Pd/C (10 wt%, 243 mg, 0.228 mmol) was added to a solution of (2S,3S)-tert-butyl-2-(benzyloxycarbonylamino)-3-((tert-butoxycarbonylamino)methyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 49, 1.40 g, 2.43 mmol) in EtOAc (50 mL). A _H₂ balloon was fitted into the flask, and the suspension was stirred overnight at room temperature. The reaction mixture was filtered through diatomaceous earth and washed with EtOAc. The filtrate was concentrated to dryness to give a crude material as a colorless oil. The crude material was subjected to chiral SFC [Chiral Pak IC column, 21x250mm, 5μm, temperature = 40℃, mobile phase = 15% isopropanol (with 0.2% _NH4OH ): _CO2 , flow rate = 4mL/min, outlet pressure = 100bar] to obtain tert-butyl(2S,3S)-2-amino-3-[(tert-butoxycarbonylamino)methyl]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 57,855mg, 80% yield, >98:2dr). ¹ HNMR (500MHz, CDCl ₃ )δ0.80(2H,t),1.19-1.33(14H,m),1.35-1.56(20H,m),1.61-1.85(2H,m),1.88-2.00(1H,m),3.10-3.31(2H,m),3.39(1H,d),5.25(1H,br s); m/z: (ES ⁺ )[M+H] ⁺ =444.

Intermediate 58: tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2- ... [[4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl]hexanoate]

HATU (142 mg, 0.373 mmol) was added to a solution of Boc-Ala-OH (70 mg, 0.37 mmol) in DMF (6 mL), and the reaction was stirred at room temperature for 10 min. Then, tert-butyl(2S,3S)-2-amino-3-[(tert-butoxycarbonylamino)methyl]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 57, 150 mg, 0.34 mmol) in DMF (2 mL) was added to the reaction. N,N-diisopropylethylamine (0.12 mL, 0.68 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with saturated _NH₄Cl aqueous solution and DCM, and the layers were separated. The aqueous layer was extracted with DCM (3 x 20 _mL ). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2-(tert-butoxycarbonylamino)propionyl]amino]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a white solid (intermediate 58, 125 mg, 60% yield). ¹ H NMR (500MHz, CDCl ₃ )δ0.71-0.82(2H,m),1.16-1.36(14H,m),1.37-1.69(34H,m),2.14-2.28(1H,m),3.01-3.10(1H,m),3.19-3 .35(1H,m), 4.21-4.36(1H,m), 4.52-4.63(1H,m), 4.66-4.80(1H,m), 5.21-5.32(1H,m), 7.13-7.25(1H,m).

Example 25: (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-aminopropionyl]amino]-6-dihydroxyboryl-hexyl acid

Tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2-(tert-butoxycarbonylamino)propionyl]amino]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 58, 125 mg, 0.204 mmol)) was dissolved in HCl (4 M, in dioxane, 7.0 mL, 28 mmol), and the reaction was heated to 50 °C and stirred for 2 h. The reaction mixture was cooled to room temperature, and the solvent was removed under reduced pressure. The resulting white solid was dissolved in 1 M HCl aqueous solution (10 mL) and _Et₂O (10 mL). Phenylboronic acid (49 mg, 0.41 mmol) was added, and the reaction was stirred at room temperature for 1 h. The reaction mixture was diluted with water and washed with _Et₂O . The aqueous layer was lyophilized and purified by ion exchange chromatography (PoraPak Rxn CX20cc column). The desired product was eluted from the column using 2.5 M ammonia/methanol. The obtained material was further purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 20% aqueous acetonitrile) to give (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-aminopropionyl]amino]-6-dihydroxyboronyl-hexanoic acid as a white solid (Example 25, 38 mg, 67% yield). ¹ H NMR (500MHz, D ₂ O)δ0.74(2H, t), 1.31(3H, d), 1.33-1.54(4H, m), 2.14-2.25(1H, m), 2.98-3.04(1H, m), 3.06-3.15(1H, m), 3.64(1H, q), 4.36(1H, d); m/z: (ES ⁺ )[M+H] ⁺ =276.

Example 26: (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-amino-3-methyl-butyryl]amino]-6-di Hydroxyboronic-hexanoic acid

Intermediate 59: tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2- ... [4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl](4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl) hexanoate

HATU (326 mg, 0.857 mmol) was added to a solution of Boc-Val-OH (186 mg, 0.857 mmol) in DMF (10 mL), and the reaction was stirred at room temperature for 10 min. Then, tert-butyl(2S,3S)-2-amino-3-[(tert-butoxycarbonylamino)methyl]-6-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)hexanoate (intermediate 57, 345 mg, 0.780 mmol) in DMF (5 mL) was added to the reaction. N,N-diisopropylethylamine (0.27 mL, 1.6 mmol) was added, and the reaction was stirred overnight at room temperature. The reaction mixture was diluted with saturated _NH₄Cl aqueous solution and DCM, and the layers were separated. The aqueous layer was extracted with DCM (3 x 40 _mL ). The combined organic matter was dried over _Na₂SO₄ , filtered, and concentrated to dryness. The crude material was purified by silica gel chromatography (hexane/EtOAc) to give tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2-(tert-butoxycarbonylamino)-3-methyl-butyryl]amino]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate as a white solid (intermediate 59,422 mg, 84% yield). ¹ HNMR (500MHz, CDCl ₃ )δ0.77(2H,m),0.90-1.04(6H,m),1.13-1.36(14H,m),1.37-1.72(31H,m),2.12-2.31(2H , m), 2.94-3.08(1H, m), 3.18-3.37(1H, m), 4.00-4.11(1H, m), 4.61(1H, brd), 4.70(1H, br d), 5.22 (1H, m), 7.08-7.20 (1H, m).

Example 26: (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-amino-3-methyl-butyryl]amino]-6-di Hydroxyboronic-hexanoic acid

Tert-butyl(2S,3S)-3-[(tert-butoxycarbonylamino)methyl]-2-[[(2S)-2-(tert-butoxycarbonylamino)-3-methyl-butyryl]amino]-6-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)hexanoate (intermediate 59,422, 0.658 mmol)) was dissolved in HCl (4 M, in dioxane, 10.0 mL, 48.0 mmol), and the reaction was heated to 50 °C and stirred for 2 h. The reaction mixture was cooled to room temperature, and the solvent was removed under reduced pressure. The resulting white solid was dissolved in 1 M HCl aqueous solution (15 mL) and _Et₂O (15 mL). Phenylboronic acid (160 mg, 1.32 mmol) was added, and the reaction was stirred at room temperature for 1 h. The reaction mixture was diluted with water and washed with _Et₂O . The aqueous layer was lyophilized and purified by ion-exchange chromatography (Silicycle SPE-R51230B-20X column). The desired product was eluted from the column using 2.5 M ammonia/methanol. The obtained material was further purified by reversed-phase chromatography (RediSep RfC18Aq, 0 to 20% aqueous acetonitrile) to give (2S,3S)-3-(aminomethyl)-2-[[(2S)-2-amino-3-methyl-butyryl]amino]-6-dihydroxyboronyl-hexanoic acid as a white solid (Example 26, 162 mg, 81% yield). ¹ H NMR (500MHz, D ₂ O)δ0.76(2H,t),0.91(3H,d),0.95(3H,d),1.28-1.52(4H,m),1.99(1H,dq),2.18 (1H, dq), 2.98-3.07 (1H, m), 3.08-3.17 (1H, m), 3.31 (1H, d), 4.37 (1H, d); m/z: (ES ⁺ )[M+H] ⁺ =304.

Example 27: Bioactivity of Examples 1-26

The inhibitory effects of Examples 1-26 on human arginase 1 and arginase 2 activities were quantified by measuring the formation of thioarginine groups by recombinant arginase 1 or arginase 2 produced by *E. coli*. Thiol groups were detected using Ellman's reagent 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB). DTNB reacts with thiols to produce a mixture of disulfides and 2-nitro-5-thiobenzoic acid (TNB), the latter being quantified by the absorbance of the anion (TNB ^2- ) at 412 nm.

The determination was performed in a transparent 384-well plate (Greiner catalog number: 781101). Examples 1-26 at different concentrations in 300 nL DMSO were dispensed into the plate using an Echo acoustic dispenser, followed by immediate plate sealing and centrifugation.

Two premixes were prepared from reagents thawed immediately before addition to the assay plate. Premix 1 contained human arginase 1 or human arginase 2 at a final concentration of 5 nM and 0.5 mM DTNB in the following assay buffer: 45 mM HEPES pH 7.5, Brij 35 (0.045% (w/v)) and 100 μM _MnCl2 . Premix 2 contained freshly thawed 0.5 mM thioarginine in the assay buffer. 15 μL of premix 1 was dispensed into the assay plate containing Examples 1–9, centrifuged, and incubated at room temperature for 30 min, followed by the addition of 15 μL of premix 2.

Centrifuge the assay plate and then read the absorbance at 412 nm using a Pherastar multimode microplate reader to collect data at time point 0 (T0). Incubate the plate at room temperature for 60 min and then read the absorbance again to collect data at time point 1 (T1). Data are obtained by subtracting the A412 signal measured at T0 (T0) from the A412 signal measured at T1 (T1). Convert the data to percentage of effect using the following equation:

Compound effect % = 100 * [(X - minimum) / (maximum - minimum)],

Where X represents the normalized value of the compound based on the minimum (mediator) and maximum (reference compound) inhibition controls.

The concentrations (i.e., _IC50 ) that inhibited activity by 50% were calculated for Examples 1-26 by plotting the percentage of effect relative to the concentration of the test compound and fitting the data using the Genedata Screener Smart fitting algorithm. The results of these determinations are shown in Table 2:

Table 2

Example 28: Bioavailability Study

Example 14 is a prodrug form of Example 1. Examples 19 to 22 and 24 to 26 are prodrugs of Example 18. The following pharmacokinetic studies were performed to demonstrate the bioavailability of Example 18 derived from Example 19. Example 19 was prepared in 0.9% w/v saline at pH 4 (adjusted with 1M HCl) for intravenous (IV) administration. The preparation was administered to two male rats (170g–250g each) via the femoral catheter at a dose of 2 mg/kg. Serial blood samples were collected from the jugular venous catheter at 0.033, 0.083, 0.167, 0.5, 1, 2, 4, 8, and 24 hours post-administration. For oral (PO) administration, Example 19 was prepared in deionized water at pH 4 (adjusted with 1M HCl) and administered to two male rats (170g–250g each) orally by gavage at a dose of 5 mg/kg. Continuous blood samples were collected via a jugular vein catheter at 0.25, 0.5, 1, 1.5, 2, 3, 4, 8, and 24 hours after administration. Plasma samples were generated from the blood using low-speed centrifugation. Single-unit calibration standards containing those from Examples 18 and 19 were prepared by adding spiked blank plasma. Samples and standards were extracted by precipitation with twice the volume of acetonitrile followed by centrifugation. The results obtained were used to determine Cl (mL/min/kg), Vdss (L/kg), Cmax (μM), AUC (μM h), tmax (h), and %F for Examples 18 and 19. Absolute bioavailability was determined by comparing the normalized AUC of the oral dose for Example 18 (when administered with Example 19) with the normalized AUC of the intravenous dose for Example 18 (when administered with Example 18). Where appropriate, the measured dose was used instead of the nominal dose in calculations. The same procedure was repeated for Examples 14, 20–22, and 24–26 in a similar manner. The results are shown in Tables 3 to 10. These results indicate that bioavailability can be improved by incorporating certain amino acid moieties as prodrugs.

Table 3

Example 19 Example 18 Cl (mL/min/kg) <![CDATA[16.40^#]]> 7.30* Vdss(L/kg) <![CDATA[0.47^#]]> 0.38* PO Cmax (μM) <![CDATA[0.66^#]]> <![CDATA[4.40^#]]> PO AUC (μM.h) <![CDATA[1.40^#]]> <![CDATA[15.6^#]]> Tmax(h) <![CDATA[0.50^#]]> <![CDATA[1.50^#]]> %F <![CDATA[8.30^#]]> <![CDATA[37.00^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 4

Example 20 Example 18 Cl (mL/min/kg) <![CDATA[12.50^#]]> 7.30* Vdss(L/kg) <![CDATA[0.21^#]]> 0.38* PO Cmax (μM) <![CDATA[0.44^#]]> <![CDATA[8.10^#]]> PO AUC (μM.h) <![CDATA[1.25^#]]> <![CDATA[30.90^#]]> Tmax(h) <![CDATA[0.75^#]]> <![CDATA[1.25^#]]> %F <![CDATA[5.10^#]]> <![CDATA[54.90^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 5

Example 21 Example 18 Cl (mL/min/kg) <![CDATA[14.10^#]]> 7.30* Vdss(L/kg) <![CDATA[0.22^#]]> 0.38* PO Cmax (μM) <![CDATA[0.23^#]]> <![CDATA[10.20^#]]> PO AUC (μM.h) <![CDATA[0.35^#]]> <![CDATA[32.40^#]]> Tmax(h) <![CDATA[0.50^#]]> <![CDATA[1.25^#]]> %F <![CDATA[1.50^#]]> <![CDATA[72.00^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 6

Example 22 Example 18 Cl (mL/min/kg) <![CDATA[13.10^#]]> 7.30* Vdss(L/kg) <![CDATA[0.20^#]]> 0.38* PO Cmax (μM) <![CDATA[0.45^#]]> <![CDATA[4.70^#<!-- 58 -->]]> PO AUC (μM.h) <![CDATA[0.92^#]]> <![CDATA[16.00^#]]> Tmax(h) <![CDATA[1.00^#]]> <![CDATA[1.75^#]]> %F <![CDATA[4.50^#]]> <![CDATA[39.00^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 7

Example 24 Example 18 Cl (mL/min/kg) <![CDATA[8.40^#]]> 7.30* Vdss(L/kg) <![CDATA[0.20^#]]> 0.38* PO Cmax (μM) <![CDATA[0.88^#]]> <![CDATA[1.30^#]]> PO AUC (μM.h) <![CDATA[2.90^#]]> <![CDATA[6.40^#]]> Tmax(h) <![CDATA[1.75^#]]> <![CDATA[2.50^#]]> %F <![CDATA[6.40^#]]> <![CDATA[11.30^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 8

Example 26 Example 18 Cl (mL/min/kg) <![CDATA[26.60^#]]> <![CDATA[7.30^*]]> Vdss(L/kg) <![CDATA[0.15^#]]> <![CDATA[0.38^*]]> PO Cmax (μM) <![CDATA[NV^#]]> <![CDATA[15.30^#]]> PO AUC (μM.h) <![CDATA[NV^#]]> <![CDATA[37.30^#]]> Tmax(h) <![CDATA[NV^#]]> <![CDATA[0.75^#]]> %F <![CDATA[NV^#]]> <![CDATA[66.30^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 9

Example 25 Example 18 Cl (mL/min/kg) <![CDATA[28.30^#]]> 7.30* Vdss(L/kg) <![CDATA[0.18^#]]> 0.38* PO Cmax (μM) <![CDATA[0.04^#]]> <![CDATA[8.83^#]]> PO AUC (μM.h) <![CDATA[NV^#]]> <![CDATA[26.20^#]]> Tmax(h) <![CDATA[0.25^#]]> <![CDATA[1.00^#]]> %F <![CDATA[NV^#]]> <![CDATA[56.00^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Table 10

Example 14 Example 1 Cl (mL/min/kg) <![CDATA[46.10^#]]> 8.26* Vdss(L/kg) <![CDATA[0.47^#]]> 0.46* PO Cmax (μM) <![CDATA[0.13^#]]> <![CDATA[3.42^#]]> PO AUC (μM.h) <![CDATA[NV^#]]> <![CDATA[15.50^#]]> Tmax(h) <![CDATA[0.25^#]]> <![CDATA[1.75^#<!-- 59 -->]]> %F <![CDATA[NV^#]]> <![CDATA[42.30^#]]>

#Observations at prodrug administration* Observations at effective load administration. No NV values are available for reporting.

Claims (9)

1. A compound having formula (II) or a pharmaceutically acceptable salt thereof: in ^R11 is selected from hydrogen and _-CH3 ; ^Y1 is -( _CH2 ) _p ; p is 1; ^R12 is selected from hydrogen, _-CH3 and -(C= ^X1 ) ^R14 , and ^R13 is hydrogen; X ¹ is O; R ¹⁴ is one of the *indicator (S) stereochemistry; R ^14a is a _C1 - _C4 alkyl group; and q is 1. 2. A compound having formula (III) or a pharmaceutically acceptable salt thereof: in R ²² is hydrogen or where * indicates (S) stereochemistry; and R ^24a is a _C1 - _C4 alkyl group. 3. A compound having formula (IV) or a pharmaceutically acceptable salt thereof: in R ¹¹ is selected from *indicator (S) stereochemistry; and R ^11a is a methyl group. 4. A compound or a pharmaceutically acceptable salt thereof, said compound being selected from: 5. A pharmaceutical composition comprising a compound as described in any one of claims 1 to 4 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier, diluent or excipient. 6. Use of the compound of any one of claims 1 to 4 or a pharmaceutically acceptable salt thereof or the pharmaceutical composition of claim 5 in the manufacture of a medicament for treating cancer, wherein the cancer is selected from renal cell carcinoma, head and neck squamous cell carcinoma, lung cancer, pancreatic cancer, colorectal cancer, breast cancer, acute myeloid leukemia, prostate cancer, gastric cancer, bladder cancer, melanoma, kidney cancer, and ovarian cancer. 7. The use as described in claim 6, wherein the lung cancer is small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), or mesothelioma. 8. Use of the compound of any one of claims 1 to 4 or a pharmaceutically acceptable salt thereof or the pharmaceutical composition of claim 5 in the manufacture of a medicament for treating inflammatory respiratory diseases selected from asthma, chronic obstructive pulmonary disease (COPD), chemically induced pulmonary fibrosis, idiopathic pulmonary fibrosis, cystic fibrosis, or combinations thereof. 9. The use as claimed in claim 8, wherein the inflammatory respiratory disease is selected from idiopathic pulmonary fibrosis, asthma, chronic obstructive pulmonary disease (COPD), and chemically induced pulmonary fibrosis.