HK40019933B - Pyridine derivatives - Google Patents

Description

Pyridine derivatives

This invention relates to organic compounds that can be used for treatment and/or prevention in mammals, and more particularly to compounds that are preferred inverse agonists of cannabinoid receptor 2.

This invention relates particularly to compounds of formula (I),

in

R ¹ is a halophenyl, cycloalkylalkoxy, alkyloxetyl alkoxy, alkoxycarbonylpyrrolidinylalkoxy, alkoxycarbonylpyrrolidinylalkoxy, alkylsulfonylphenylalkoxy, haloalkoxy, (alkyl)(halo)cycloalkylalkoxy, benzotriazolylalkoxy, halopyridylalkoxy, or halopyridyl.

^R2 is a halogen, cycloalkyl, haloalkyl, cycloalkylalkoxy, 2-oxa-6-azaspiro[3.3]heptyl or phenylalkoxy;

^R3 is -C(O)-NH-C( ^R4R5 ) _m ( ^CH2 ) _n ^-R6 _or alkyloxadiazole group;

^R4 and ^R5 are independently selected from hydrogen, alkyl, hydroxyalkyl, haloalkyl, azacyclobutyl, cycloalkylalkyl, and cycloalkyl;

R ⁶ is hydroxyl, hydroxycycloalkyl, alkoxycarbonyl, alkoxycycloalkyl, aminocarbonyl, phenyl, pyridyl, alkyl-1,2,4-oxadiazolyl, alkylaminocarbonyl, haloalkyl or alkyl-1,3,4-oxadiazolyl;

m is 0 or 1; and

n is 0 or 1;

Or its medicinal salts or esters.

In particular, compounds of formula (I) can be used to treat or prevent pain, neuropathic pain, asthma, osteoporosis, inflammation, psychiatric diseases, psychosis, oncology, encephalitis, malaria, allergy, immune disorders, arthritis, gastrointestinal disorders, psychiatric disorders, rheumatoid arthritis, psychosis, or allergic reactions.

Cannabinoid receptors are a class of cell membrane receptors belonging to the G protein-coupled receptor superfamily. Currently, two known subtypes exist, called cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). CB1 receptors are primarily expressed in the central nervous system (i.e., the amygdala, cerebellum, and hippocampus) and expressed in smaller amounts in the periphery. The CB2 receptor, encoded by the CNR2 gene, is primarily expressed on cells of the immune system, such as macrophages and T cells (Ashton, J.C. et al. Curr Neuropharmacol 2007, 5(2), 73-80; Miller, A.M. et al. Br J Pharmacol 2008, 153(2), 299-308; Centonze, D. et al. Curr PharmDes 2008, 14(23), 2370-42) and in the peripheral system of the gastrointestinal tract (Wright, K.L. et al. Br J Pharmacol 2008, 153(2), 263-70). The CB2 receptor is also widely distributed in the brain, where it is primarily found on microglia rather than neurons (Cabral, G.A. et al. Br J Pharmacol 2008, 153(2): 240-51).

Interest in CB2 receptor ligands has steadily increased over the past decade (currently 30-40 patent applications per year). Evidence from various sources supports the view that lipid endocannabinoid signaling via the CB2 receptor represents an aspect of protective medical devices in mammals (Pacher, P. Prog Lipid Res 2011, 50, 193). Modulation of the CB2 receptor by selective agonists or inverse agonists/antagonists (depending on the disease and its stage) holds unique therapeutic potential in a wide range of diseases. For CB2 inverse agonists/antagonists, therapeutic potential has been shown for many pathological conditions, including pain (Pasquini, S.J Med Chem 2012, 55(11): 5391), neuropathic pain (Garcia-Gutierrez, M.S.Br J Pharmacol 2012, 165(4): 951), and mental illness (Garcia-Gutierrez, M.S.Br J Pharmacol 2012, 165(4): 951). 012, 165(4): 951), mental illness (Garcia-Gutierrez, M.S.Br JPharmacol 2012, 165(4): 951), osteoporosis and inflammation (Sophocleous, A.Calcif Tissue Int 2008, 82(Suppl.1): Abst OC 18), mental illness and psychosis (Garcia-Gutierrez, M.S.Br JPharmacol 2 012, 165(4): 951), tumors (Preet, A. Cancer Prev Res 2011, 4: 65), encephalitis and malaria (Zimmer, A. WO 2011045068), allergies and inflammation (Ueda, Y. Life Sci 2007, 80(5): 414), encephalitis and malaria (Zimmer, WO 2011045068), asthma (Lunn, C.A.J Pharmacol Exp Ther 2006, 316(2): 780), immune disorders (Fakhfouri, G. Neuropharmacology 2012, 63(4): 653), rheumatoid arthritis (Chackalamannil, S.US 7776889), arthritis (Lunn, C.A.J Pharmacol Exp Ther 2006, 316(2): 780), and gastrointestinal disorders (Barth, F.FR 2887550).

The compounds of this invention bind to and modulate the CB2 receptor and have lower CB1 receptor activity.

In this specification, the term "alkyl" refers, alone or in combination, to a straight-chain or branched alkyl group having 1 to 8 carbon atoms, particularly a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and even more particularly a straight-chain or branched alkyl group having 1 to 4 carbon atoms. Examples of straight-chain and branched C1-C8 alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, isopentyl, isohexyl, isoheptyl, and isooctyl, especially methyl, ethyl, propyl, butyl, and pentyl. Specific examples of alkyl groups are methyl, ethyl, isopropyl, butyl, isobutyl, tert-butyl, and pentyl. In compounds of formula (I), methyl, ethyl, tert-butyl, and isobutyl are specific examples of alkyl groups.

The term "cycloalkyl" refers, alone or in combination, to a cycloalkyl ring having 3 to 8 carbon atoms, and particularly to a cycloalkyl ring having 3 to 6 carbon atoms. Examples of cycloalkyl are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Specific examples of "cycloalkyl" are cyclopropyl and cyclohexyl.

The term "alkoxy", alone or in combination, refers to a group having the formula alkyl-O- (wherein the term "alkyl" has the meaning previously given), such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, and tert-butoxy. The particular "alkoxy" refers to methoxy and tert-butoxy.

The term "oxygen group" refers to the -O- group, either alone or in combination.

The term "oxo" alone or in combination refers to the =O group.

The term "halogen" or "halogenated" alone or in combination means fluorine, chlorine, bromine or iodine, and especially fluorine, chlorine or bromine, and more particularly fluorine and chlorine. The term "halogenated" in combination with another group means that the group is substituted by at least one halogen, especially by 1 to 5 halogens, and especially by 1 to 4 halogens, i.e., substituted by 1, 2, 3 or 4 halogens.

The term "haloalkyl" refers, alone or in combination, to an alkyl group substituted with at least one halogen, particularly substituted with 1 to 5 halogens, and especially substituted with 1 to 3 halogens. Particular examples of "haloalkyl" are trifluoromethyl and trifluoroethyl, particularly trifluoromethyl.

The term "haloalkoxy" or "haloalkyloxy" refers, alone or in combination, to an alkoxy group substituted with at least one halogen, particularly substituted with 1 to 5 halogens, and especially substituted with 1 to 3 halogens. A particular "haloalkoxy" is trifluoroethyloxy.

The terms “hydroxyl” and “hydroxyl”, alone or in combination, refer to the -OH group.

The term "carbonyl" refers, alone or in combination, to a -C(O)- group.

The term "amino" refers, alone or in combination, to a primary amino group (-NH2), a secondary amino group (-NH-), or a tertiary amino group (-N-).

The term "aminocarbonyl" refers, alone or in combination, to the -C(O) _-NH2 , -C(O)-NH-, or -C(O)-NH- group.

The term "sulfonyl" refers, alone or in combination, to the _-SO2 group.

The term "medicinal salt" refers to those salts that retain the biological effectiveness and properties of free bases or free acids, and which are not biologically or otherwise unsuitable. These salts are formed using acids such as inorganic acids like hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, especially hydrochloric acid, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid, and N-acetylcysteine. Furthermore, these salts can be prepared by adding an inorganic or organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, sodium, potassium, lithium, ammonium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of the following: primary, secondary, and tertiary amines; substituted amines (including naturally occurring substituted amines); cyclic amines; and basic ion exchange resins such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, lysine, arginine, N-ethylpiperidine, piperidine, and polyamine resins. Compounds of formula (I) may also exist in zwitterionic form. Particularly preferred pharmaceutical salts of compounds of formula (I) are salts of hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, and methanesulfonic acid.

"Pharmaceutical ester" means that a compound of general formula (I) can be derived at a functional group to provide a derivative that can be converted back to the parent compound in vivo. Examples of such compounds include physiologically acceptable and metabolically unstable ester derivatives, such as methoxymethyl ester, methylthiomethyl ester, and neopentyloxymethyl ester. Furthermore, any physiologically acceptable equivalent of a compound of general formula (I) that can produce a parent compound of general formula (I) in vivo, similar to metabolically unstable esters, is within the scope of this invention.

If one of the starting materials or compounds of formula (I) contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group can be introduced prior to the critical step using methods known in the art (e.g., as described in T.W. Greene and P.G.M. Wuts, 3rd edition, 1999, Wiley, New York). Such protecting groups can be removed at a later stage of the synthesis using standard methods described in the literature. Examples of protecting groups are tert-butoxycarbonyl (Boc), 9-fluorenylmethyl carbamate (Fmoc), 2-trimethylsilylethyl carbamate (Teoc), benzyloxycarbonyl (Cbz), and p-methoxybenzyloxycarbonyl (Moz).

The compound of formula (I) may contain several asymmetric centers and may exist in the following forms: optically pure enantiomers, mixtures of enantiomers (such as, for example, racemates), mixtures of diastereomers, racemates of diastereomers, or mixtures of racemates of diastereomers.

The term "asymmetric carbon atom" refers to a carbon atom with four different substituents. According to the Cahn-Ingold-Prelog rule, an asymmetric carbon atom can be either "R" or "S" configuration.

This invention particularly relates to:

A compound of formula (I), wherein ^R1 is alkoxycarbonylpyrrolidinylalkoxy, alkoxycarbonylpyrrolidinylalkoxy, alkylsulfonylphenylalkoxy, (alkyl)(halo)cycloalkylalkoxy, benzotriazolylalkoxy, halopyridylalkoxy, or halopyridyl.

A compound of formula (I), wherein ^R1 is tert-butoxycarbonylpyrrolidinylmethoxy, butoxycarbonylpyrrolidinylmethoxy, methanesulfonylphenylmethoxy, (methyl)(difluoro)cyclopropylmethoxy, benzotriazolyloxy, fluoropyridinylmethoxy, or fluoropyridinyl.

A compound of formula (I), wherein ^R2 is a haloalkyl, cycloalkylalkoxy, 2-oxa-6-azaspirocyclic[3.3]heptyl or phenylalkoxy;

A compound of formula (I), wherein ^R2 is hydrogen, trifluoromethyl, cyclopropylmethoxy, 2-oxa-6-azaspirocyclic[3.3]heptyl or phenylmethoxy;

A compound of formula (I), wherein ^R3 is -C(O)-NH-C(O)-NH-C( ^R4R5 ) _m ( ^CH2 ) _n ^-R6 _or tert-butyloxadiazolyl;

A compound of formula (I), wherein ^R6 is a hydroxyl, alkoxycarbonyl, aminocarbonyl, or alkylaminocarbonyl group; and

A compound of formula (I), wherein ^R6 is a hydroxyl, methoxycarbonyl, aminocarbonyl, or methylaminocarbonyl.

The present invention also relates to compounds of formula (I), said compounds being selected from:

5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide;

4-(4-Chlorophenyl)-5-(Cyclopropylmethoxy)-N-[(1R,2S)-2-hydroxycyclohexyl]pyridine-2-carboxamide;

4-(4-Chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1S,2R)-2-hydroxycyclohexyl]pyridine-2-carboxamide;

2-[[4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester;

2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester;

4-(4-Chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1R,2S)-2-methoxycyclohexyl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2-hydroxy-1-phenylethyl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(1S)-2,2,2-trifluoro-1-pyridin-2-ylethyl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2,2,2-trifluoro-1-pyridin-3-ylethyl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide;

5-Chloro-4-(cyclopropylmethoxy)-N-[(2R)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide;

5-Cyclopropyl-N-[(2S)-3,3-Dimethyl-1-(methylamino)-1-oxobut-2-yl]-4-[(3-methyloxetanebut-3-yl)methoxy]pyridine-2-carboxamide;

6-[6-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-4-(cyclopropylmethoxy)pyridin-3-yl]-2-oxa-6-azaspirocyclic[3.3]heptane;

(2S)-2-[[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxymethyl]pyrrolidine-1-carboxylic acid tert-butyl ester;

(3R)-3-[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxypyrrolidine-1-carboxylic acid tert-butyl ester;

5-tert-butyl-3-[5-cyclopropyl-4-[(3-methylsulfonylphenyl)methoxy]pyridin-2-yl]-1,2,4-oxadiazole;

N-[1-(azacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl]-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridine-2-carboxamide;

2-[[5-cyclopropyl-4-[(3-methyloxetane-3-yl)methoxy]pyridine-2-carbonyl]amino]-2-ethylbutyrate ethyl ester;

5-Chloro-N-[1-Cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-[(2,2-difluoro-1-methylcyclopropyl)methoxy]pyridine-2-carboxamide;

4-(benzotriazol-1-yloxy)-N-[1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-5-(trifluoromethyl)pyridine-2-carboxamide;

N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide; and

N-[(2S)-1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-(6-fluoropyridin-3-yl)-5-phenylmethoxypyridin-2-carboxamide.

The present invention also particularly relates to compounds of formula (I), said compounds being selected from:

5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide;

2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester;

5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]pyridine-2-carboxamide;

5-Cyclopropyl-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]-4-[(3-methyloxetanebut-3-yl)methoxy]pyridine-2-carboxamide; and

N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide.

In the following schemes and descriptions, unless otherwise specified, ^R1 to ^R6 have the meanings of ^R1 to ^R6 as defined above.

The preparation of compounds of formula (I) of the present invention can be carried out via sequential or convergent synthetic routes. The synthesis of compounds of the present invention is shown in the following schemes. The techniques required for carrying out the reactions and purifying the resulting products are known to those skilled in the art. Unless otherwise indicated, the substituents and designations used in the following description of the methods have the meanings given herein. More specifically, compounds of formula (I) can be prepared by the methods given below, by the methods given in the examples, or by similar methods. Suitable reaction conditions for the various reaction steps are known to those skilled in the art. Furthermore, for the reaction conditions described in the literature affecting the reactions, see, for example: *Comprehensive Organic Transformations: A Guide to Functional Group Preparations*, 2nd edition, Richard C. Larock, John Wiley & Sons, New York, NY. 1999). We have found it suitable to carry out the reactions with or without a solvent. There are no particular limitations on the nature of the solvent to be used, as long as it does not adversely affect the reactions involved or the reagents and can at least partially dissolve the reagents. The described reaction can occur over a wide range of temperatures, and a precise reaction temperature is not critical to the invention. It is suitable to carry out the reaction in the temperature range of -78°C to reflux. The reaction time can also vary widely, depending on many factors, particularly the reaction temperature and the nature of the reagents. However, time periods of 0.5 hours to several days are generally sufficient to generate the intermediates and compounds described. The reaction sequence is not limited to the sequence shown in the specification; however, the order of reaction steps can be arbitrarily changed depending on the starting materials and their respective reactivity. The starting materials are commercially available or can be prepared by methods similar to those given below, by methods described in the references cited in the specification or examples, or by methods known in the art.

The synthesis of compounds having general structure I can be carried out, for example, according to the following scheme.

According to the procedure in Scheme 1, compound AA (6-chloro-5-hydroxy-4-iodo-2-pyridinyl alcohol, CAS RN208519-37-3) can be used as a starting material. AA is commercially available, or alternatively can be prepared by two-step sequential preparation from 2-chloro-3-pyridinol according to a literature procedure, or by other procedures known to those skilled in the art.

Option 1

Compound AB can be prepared from AA by reacting with a suitably substituted primary or secondary alkyl halide R2'-X or primary or secondary trifluoromethanesulfonate alkyl ester R2' ^- OTf in the presence of a base such as sodium hydride, in an inert solvent such as hexamethylphosphoramide, at a temperature from room temperature to solvent reflux temperature (preferably at a high temperature, e.g., 120°C) ( ^{R2 '} = cycloalkylalkyl or phenylalkyl; step a).

Compound AD can be prepared from AB by coupling a suitably substituted aryl metal substance having the formula AC (preferably an arylboronic acid or arylboronic ester) with AB in the presence of a suitable catalyst (preferably a palladium catalyst, and more preferably a mixture of palladium(II) acetate/triphenylphosphine or palladium(II) chloride-dppf (1,1'-bis(diphenylphosphino)ferrocene) complex) and a base (preferably triethylamine or sodium carbonate) in an inert solvent such as dimethylformamide or toluene (step b).

Compound AE can be obtained by selective hydrogenation of compound AC using methods known in the art, for example by hydrogenation in acetic acid with zinc in the presence of tetramethylammonium bromide at a temperature from room temperature to solvent reflux temperature (preferably at 50°C) (step c).

Compound AF can be prepared from AE by oxidation using a large number of possible methods known in the art. A suitable method is to catalytically oxidize (step d) using a TEMPO mixture of sodium chlorite and sodium hypochlorite in a suitable solvent mixture (preferably in an acetonitrile/phosphate buffer mixture) at a temperature from room temperature to high temperature (preferably 35°C).

Compound I can be prepared by _a suitable amide bonding reaction from acid AF and the corresponding amine AG (R = -C( ^R₄R₅ ) _m ( ^CH₂ ) _n - ^R₆ ). These reactions are known in the art. For example, coupling agents such as N,N'-carbonyl-diimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), and O-benzotriazol-1-yl-N,N,N',N'-tetramethylureon tetrafluoroborate (TBTU) can be used to achieve such a transformation (step e). A suitable method is to use, at room temperature, an inert solvent such as dimethylformamide, and a base such as Hünig's base (N-ethyldiisopropylamine).

If the starting material, i.e., one of the compounds of formula AA, AC, or AG, contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group (P) can be introduced prior to the critical step using methods known in the art (e.g., as described in T.W. Greene et al., Protective Groups in Organic Chemistry, John Wiley and Sons Inc. New York 1999, 3rd edition). Such protecting groups can be removed at a later stage of the synthesis using standard methods known in the art.

If one or more compounds of formulas AA to AC or AG contain a chiral center, then compounds of formula I can be obtained as diastereomers or mixtures of enantiomers, which can be separated by methods known in the art, such as (chiral) HPLC or crystallization. Racemic compounds can be separated as their enantiomers, for example, by crystallization via diastereomeric salts, or by enantiomer separation using chiral adsorbents or chiral eluents via specific chromatographic methods.

According to the procedure of Scheme 2, compound BA (X = Cl, Br, I) can be used as a starting material (e.g., 5-chloro-4-iodo-2-pyridinecarboxylic acid (CAN 120643-06-3, for compounds in which R ² = Cl). BA is commercially available, described in the literature, and can be synthesized by those skilled in the art, or can be synthesized as described in the experimental section.

Option 2

Compound BC can be prepared from BA by reaction with a suitably substituted primary or secondary alcohol BB in the presence of a base such as potassium tert-butoxide, in an inert solvent such as dimethylformamide or tetrahydrofuran, at a temperature ranging from room temperature to solvent reflux temperature (especially at a high temperature such as, for example, 80°C) (step a).

Compounds of formula I can be prepared by suitable amide bonding reactions from BC and the corresponding amines of formula AG (R ₌ -C( ^R₄R₅ ) _m ( ^CH₂ ) _n - ^R₆ ). These reactions are known in the art. For example, coupling agents such as N,N'-carbonyl-diimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), O-benzotriazole-1-yl-N,N,N',N'-tetramethylureonium tetrafluoroborate (TBTU), and O-benzotriazole-N,N,N',N'-tetramethylureonium hexafluorophosphate (HBTU) can be used to achieve such a conversion (step b). A suitable method is to use, for example, HBTU and a base such as DIEA in an inert solvent such as, for example, dimethylformamide, at room temperature.

Amine AG is commercially available and described in the literature. It can be synthesized by those skilled in the art or as described in the experimental section.

If one of the starting materials, compounds of formula BA, BB, or AG, contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group (P) can be introduced prior to the critical step using methods known in the art (e.g., as described in T.W. Greene et al., Protective Groups in Organic Chemistry, John Wiley and Sons Inc. New York 1999, 3rd edition). Such protecting groups can be removed at a later stage of the synthesis using standard methods known in the art.

If one or more compounds of formulas BA to BB or AG contain a chiral center, then compounds of formula I can be obtained as diastereomers or mixtures of enantiomers, which can be separated by methods known in the art, such as (chiral) HPLC or crystallization. Racemic compounds can be separated as their enantiomers, for example, by crystallization via diastereomeric salts, or by enantiomer separation using chiral adsorbents or chiral eluents via specific chromatographic methods.

According to the procedure of Scheme 3, compound CA can be used as a starting material. CA is commercially available, described in the literature, and can be synthesized by those skilled in the art or as described in the experimental section.

Option 3

Compound CB can be prepared from CA by reaction with a suitably substituted alcohol as described in the claims (step a), with or without an inert solvent such as dimethylformamide, in the presence of a base such as sodium hydride, at a temperature ranging from room temperature to solvent reflux temperature. Optionally, this step can also be carried out at a later position in the synthesis, for example after the formation of oxadiazole as described in step g.

The conversion of compound CB to compound CC can be prepared by coupling a suitably substituted cycloalkyl metal substance (e.g., trifluoroborate [ _BF3 ] ^{-K +} , borate B(OH)2, or pinacol ester of borate) (step b) in the presence of a palladium catalyst such as palladium(II) acetate/butyl- ₁ -adamantylphosphine and a base such as cesium carbonate, in an inert solvent such as toluene, at a temperature from 50°C to the solvent boiling temperature; or by coupling an arylboronic acid or arylboronic ester in the presence of a suitable catalyst (particularly a palladium catalyst, and more particularly a mixture of palladium(II) acetate/triphenylphosphine or palladium(II) chloride-dppf (1,1'-bis(diphenylphosphino)ferrocene) complex) and a base such as triethylamine, sodium carbonate, or potassium phosphate, in an inert solvent such as dimethylformamide, toluene, tetrahydrofuran, acetonitrile, or dimethoxyethane.

CC (X = Cl, Br, I) can be selectively halogenated at position 2 to obtain CD, for example by treating CC with N,N-dimethylethanolamine and butyllithium, followed by the addition of a bromine source such as 1,2-dibromotetrachloroethane (step c).

Compound CE can be prepared from CD by adding a cyanide source such as zinc cyanide or copper cyanide in a solvent such as DMF or dioxane and refluxed to the solvent boiling temperature, in the presence of a palladium catalyst such as tetra(triphenylphosphine)palladium or tri(dibenzylideneacetone)dipalladium(0) and dppf (step d).

The hydrolysis of compound CE yields pyridinecarboxylic acid CF, and can be carried out under acidic or alkaline conditions known to those skilled in the art, for example using an aqueous hydrochloric acid solution at 100°C (step e).

The cyclization of compound I can be carried out by amide coupling methods known to those skilled in the art, using a commercially available carboxylic acid with appropriate substitution to obtain intermediate CF[Int] (step f), followed by heating in a high-boiling solvent such as DMF until cyclization to an oxadiazole ring (step g).

If one of the starting materials, compounds of formula CA, or reagents used in steps a, b, or f contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group (P) can be introduced prior to the critical step using methods known in the art (e.g., as described in T.W. Greene et al., Protective Groups in Organic Chemistry, John Wiley and Sons Inc. New York 1999, 3rd edition). Such protecting groups can be removed at a later stage of the synthesis using standard methods known in the art.

If one or more compounds of formulas CA to CF contain a chiral center, then compounds of formula I can be obtained as diastereomers or mixtures of enantiomers, which can be separated by methods known in the art, such as (chiral) HPLC or crystallization. Racemic compounds can be separated as their enantiomers, for example, by crystallization via diastereomeric salts, or by enantiomer separation using chiral adsorbents or chiral eluents via specific chromatographic methods.

The present invention also relates to a method for preparing a compound of formula (I), the method comprising:

(a) Compound of formula (A)

The reaction occurs in the presence of _NH₂R , a coupling agent that forms an amide bond, and a base; or

(b) Compounds of the heating form (B)

Where R is -C( ^R₄R₅ ) _m ( ^CH₂ ) _n ^-R₆ _and ^R₁ to ^R₆ are as defined above.

Examples of coupling agents that form amide bonds are N,N'-carbonyl-diimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), O-benzotriazole-1-yl-N,N,N',N'-tetramethylureonium tetrafluoroborate (TBTU), and O-benzotriazole-N,N,N',N'-tetramethylureonium hexafluorophosphate (HBTU).

Examples of suitable bases are tertiary amine bases such as triethylamine, N-methylmorpholine, N,N-diisopropylethylamine, or 4-(dimethylamino)-pyridine.

In step (a), the reaction temperature is, for example, room temperature.

A suitable method for step (a) is to use, for example, TBTU and a base such as N-ethyl-N-isopropylprop-2-amine in an inert solvent such as, for example, dimethylformamide, at room temperature.

In step (b), heating is performed at the boiling point of a high-boiling solvent such as toluene or DMF. For example, heating can be performed at a temperature above 100°C.

Another embodiment of the invention provides pharmaceutical compositions or medicaments comprising the compounds of the invention and therapeutically inert carriers, diluents, or excipients, and methods for preparing such compositions and medicaments using the compounds of the invention. In one example, the compound of formula (I) can be formulated by mixing it with a physiologically acceptable carrier (i.e., a carrier that is non-toxic to the recipient at the dosage and concentration used in galenine formulations) at ambient temperature, at a suitable pH, and with the desired purity. The pH of the formulation depends primarily on the specific application and the concentration of the compound, but is preferably anywhere in the range of about 3 to about 8. In one example, the compound of formula (I) is formulated in acetate buffer at pH 5. In another embodiment, the compound of formula (I) is sterile. The compound can be stored, for example, as a solid or amorphous composition, as a lyophilized formulation, or as an aqueous solution.

The composition is formulated, administered, and applied in accordance with good medical practice. Factors considered in this context include the specific condition being treated, the specific mammal being treated, the individual patient's clinical condition, the cause of the condition, the delivery site of the drug, the method of administration, the schedule of administration, and other factors known to the medical practitioner.

The compounds of this invention can be administered by any suitable manner, including oral, topical (including oral and sublingual), rectal, vaginal, percutaneous, parenteral, subcutaneous, intraperitoneal, intrapulmonary, intradermal, intrathecal, epidural, and intranasal administration, as well as intralesional administration (if required for local treatment). Parenteral administration includes intramuscular, intravenous, intraarterial, intraperitoneal, or subcutaneous administration.

The compounds of the present invention can be administered in any convenient form, such as tablets, powders, capsules, solutions, dispersants, suspensions, syrups, sprays, suppositories, gels, emulsions, patches, etc. Such compositions may contain conventional components of pharmaceutical preparations, such as diluents, carriers, pH adjusters, sweeteners, fillers, and other active agents.

Typical formulations are prepared by mixing the compounds of the present invention with a carrier or excipient. Suitable carriers and excipients are well known to those skilled in the art and are described in detail, for example, in Ansel, Howard C. et al., Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems. Philadelphia: Lippincott, Williams & Wilkins, 2004; Gennaro, Alfonso R. et al., Remington: The Science and Practice of Pharmacy. Philadelphia: Lippincott, Williams & Wilkins, 2000; and Rowe, Raymond C. Handbook of Pharmaceutical Excipients. Chicago, Pharmaceutical Press, 2005. The formulation may also contain one or more buffers, stabilizers, surfactants, wetting agents, lubricants, emulsifiers, suspending agents, preservatives, antioxidants, opacifiers, flow aids, processing aids, colorants, sweeteners, flavorings, diluents, and other known additives to provide an elegant presentation of the medicine (i.e., the compound of the present invention or a pharmaceutical composition thereof) or to aid in the preparation of a pharmaceutical product (i.e., a drug).

Therefore, the present invention also relates to:

A compound of formula (I) which is used as a therapeutically active substance;

A pharmaceutical composition comprising a compound of formula (I) and a therapeutically inert carrier;

The use of compounds of formula (I) for the treatment or prevention of pain, neuropathic pain, asthma, osteoporosis, inflammation, mental illness, psychosis, tumors, encephalitis, malaria, allergic reactions, immune disorders, arthritis, gastrointestinal disorders, mental illness, rheumatoid arthritis, psychosis or allergic reactions.

The use of compounds of formula (I) for the preparation of medicaments for the treatment or prevention of pain, neuropathic pain, asthma, osteoporosis, inflammation, mental illness, psychosis, tumors, encephalitis, malaria, allergic reactions, immune disorders, arthritis, gastrointestinal disorders, mental illness, rheumatoid arthritis, psychosis, or allergic reactions.

A compound of formula (I) for the treatment or prevention of pain, neuropathic pain, asthma, osteoporosis, inflammation, mental illness, psychosis, tumors, encephalitis, malaria, allergic reactions, immune disorders, arthritis, gastrointestinal disorders, mental illness, rheumatoid arthritis, psychosis, or allergic reactions.

A method for treating or preventing pain, neuropathic pain, asthma, osteoporosis, inflammation, mental illness, psychosis, tumor, encephalitis, malaria, allergic reactions, immune disorders, arthritis, gastrointestinal disorders, mental illness, rheumatoid arthritis, psychosis, or allergic reactions, the method comprising administering an effective amount of a compound of formula (I) to a patient in need.

The present invention will now be described using the following embodiments, which are not limiting in nature.

Example

abbreviation

BINAP = 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl; CAN = Chemical Abstracts Service Number; DMF = dimethylformamide; DMSO = dimethyl sulfoxide; EtOAc = ethyl acetate; HATU = 2-(3H-[1,2,3]triazolo[4,5-b]pyridin-3-yl)-1,1,3,3-tetramethylisourea-6-fluorophosphate (V); HPLC = LC = high performance liquid chromatography; MS = mass spectrometry; TBTU = O-(benzotriazol-1-yl)-N,N,N’,N’-tetramethyl-urea-6-tetrafluoroborate; THF = tetrahydrofuran; TLC = thin-layer chromatography.

Example 1

5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide

a) [6-chloro-5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-2-pyridyl]methanol

Under a nitrogen atmosphere, a suspension of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II)x CH₂Cl₂ (1∶1) (180 mg, 220 μmol), 2,4-dichlorophenylboronic acid (927 mg, 4.9 mmol; CAN 68716-47-2), and a 2 M aqueous solution of _Na₂CO₃ (4.4 mL, 8.8 mmol) were added to a 15 _mL toluene solution of [ ₆ -chloro- _5- (cyclopropylmethoxy)-4-iodo-2-pyridyl]methanol (1.5 g, 4.4 mmol; CAN 1364677-02-0). The mixture was stirred at 90 °C for 20 h, cooled to ambient temperature, and poured onto a Chem Elut column (Varian, 20 g). The column was washed with EtOAc (50 mL). The solvent was removed under reduced pressure, and the residue was purified by column chromatography (silica gel, 70 g, EtOAc/heptane) to obtain the title compound (1.5 g, 95%) as a yellow oil, LC-MS: 357.9 [MH ⁺ ].

b) [5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-2-pyridyl]methanol

Under an argon atmosphere, tetramethylammonium bromide (6 mg, 42 μmol) was added to a solution of [6-chloro-5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-2-pyridyl]methanol (1.5 g, 4.2 mmol) in 95% acetic acid (4.2 mL). The solution was heated to 40 °C. Over 2 hours, activated zinc powder (820 mg, 12.5 mmol) was added in five portions. The mixture was stirred at 50 °C for 17 hours, cooled to ambient temperature, poured into water (50 mL), and adjusted to pH 14 by adding 2N NaOH aqueous solution (30 mL). The mixture was filtered with diatomaceous earth and extracted with EtOAc (200 mL). The layers were separated, and the aqueous layer was extracted twice more with EtOAc (2 x 100 mL). The combined extracts were dried over sodium sulfate, filtered, and the filtrate was dried under reduced pressure. The crude product was purified by column chromatography (silica gel, 90 g, 50% to 100% EtOAc in heptane) to obtain the title compound (800 mg, 59%) as yellow crystals, LC-MS: 324.1 [MH ⁺ ].

c) 5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)pyridine-2-carboxylic acid

Under an argon atmosphere, a solution of tetrabutylammonium permanganate (2.6 g, 7.22 mmol) in pyridine (10 mL) was added to a solution of [5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-2-pyridyl]methanol (780 mg, 2.41 mmol) in pyridine (10 mL). The mixture was stirred at 80 °C for 1 hour, cooled to ambient temperature, and poured into ice water (250 mL). _A saturated aqueous solution of NaHSO₃ (25 mL) and an aqueous solution of 2N HCl (200 mL) were added. The mixture was extracted with ethyl acetate (2 x 250 mL). The combined extracts were dried over sodium sulfate, filtered, and the filtrate was evaporated to dryness to obtain the title compound (780 mg, 96%) as a light brown solid, LC-MS: 336.1 [MH ^- ].

d) 5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide

To a solution of 5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)pyridine-2-carboxylic acid (100 mg, 296 μmol) in DMF (4 mL), TBTU (104 mg, 325 μmol), N,N-diisopropylethylamine (191 mg, 253 μL, 1.48 mmol) and L-leucine (39 mg, 43 μL, 325 μmol; CAN 7533-40-6) were added. The mixture was shaken at 380 rpm for 16 hours at ambient temperature. The solvent was removed under vacuum, and the crude product was purified by column chromatography (silica gel, 20 g, heptane/EtOAc) to obtain the title compound (102 mg, 79%) as a colorless foam, LC-MS: 437.1 [MH ⁺ ].

Example 2

4-(4-Chlorophenyl)-5-(Cyclopropylmethoxy)-N-[(1R,2S)-2-hydroxycyclohexyl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carboxylic acid (200 mg, 658 μmol; CAN 1018782-76-7) was reacted with (1S,2R)-2-amino-cyclohexanol hydrochloride (110 mg, 724 μmol; CAN 200352-28-9) in the presence of TBTU and N,N-diisopropylethylamine to give the title compound (236 mg, 89%) as a white foam, LC-MS: 401.1628 [MH ⁺ ].

Example 3

4-(4-Chlorophenyl)-5-(Cyclopropylmethoxy)-N-[(1S,2R)-2-hydroxycyclohexyl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carboxylic acid (200 mg, 658 μmol; CAN 1018782-76-7) was reacted with (1R,2S)-2-amino-cyclohexanol hydrochloride (110 mg, 724 μmol; CAN 190792-72-4) in the presence of TBTU and N,N-diisopropylethylamine to give the title compound (236 mg, 89%) as a white solid, LC-MS: 401.1636 [MH ⁺ ].

Example 4

2-[[4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester

Similar to the procedure described in Example 1d, 4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carboxylic acid (200 mg, 658 μmol; CAN 1018782-76-7) was reacted with methyl 2-amino-2-ethyl-butyrate hydrochloride (132 mg, 724 μmol; CAN 92398-54-4) in the presence of TBTU and N,N-diisopropylethylamine to give the title compound (264 mg, 93%) as a white solid, LC-MS: 431.1742 [MH ⁺ ].

Example 5

2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester

a) [6-chloro-5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)-2-pyridyl]methanol

Similar to the procedure described in Example 1a, [6-chloro-5-(cyclopropylmethoxy) _-4- iodo- ₂ -pyridyl]methanol (23 g, 68 mmol; CAN 1364677-02-0) was reacted with 3,4-dichlorophenylboronic acid ( _12.9 g, 68 mmol; CAN 151169-75-4) in the presence of [ _1,1' -bis(diphenylphosphino)ferrocene]dichloropalladium(II)xCH₂Cl₂ (1:1) and Na₂CO₃ to give the title compound (23.6 g, 97%) as a grayish-white solid, LC-MS: 358.0161 [ ^MH⁺ ].

b) [5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)-2-pyridyl]methanol

Similar to the procedure described in Example 1b, [6-chloro-5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)-2-pyridyl]methanol (23.6 g, 66 mmol) was reacted with tetramethylammonium bromide and activated zinc powder to obtain the title compound (18.6 g, 87%) as a light brown solid, LC-MS: 324.0551 [MH ⁺ ].

c) 5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carboxylic acid

Similar to the procedure described in Example 1c, [5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)-2-pyridyl]methanol (18.6 g, 57 mmol) was oxidized with tetrabutylammonium permanganate in pyridine to give the title compound (19.1 g, 98%) as a grayish-white solid, LC-MS: 336.1 [MH ^- ].

d) Methyl 2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate

Similar to the procedure described in Example 1d, 5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carboxylic acid (200 mg, 591 μmol) was reacted with methyl 2-amino-2-ethyl-butyrate hydrochloride (118 mg, 651 μmol; CAN 92398-54-4) in the presence of TBTU and N,N-diisopropylethylamine to obtain the title compound (238 mg, 86%) as a white solid, LC-MS: 465.1333 [MH ⁺ ].

Example 6

2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester

To an ice-cold solution of 4-(4-chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1R,2S)-2-hydroxycyclohexyl]pyridine-2-carboxamide (70 mg, 175 μmol; Example 2) in THF (5 mL), a 60% dispersion of sodium hydride in mineral oil (8.4 mg, 210 μmol) was added. The mixture was stirred at ambient temperature for 1 hour. Iodimethane (24.8 mg, 10.9 μL, 175 μmol) was added, and stirring was continued for 23 hours. The suspension was poured into ice water and extracted with EtOAc (2 x 60 mL). The combined extracts were dried over sodium sulfate, filtered, and the filtrate was dried. The crude product was purified by column chromatography (silica gel, 10 g, EtOAc/heptane) to obtain the title compound (28 mg, 39%) as a colorless oil, LC-MS: 415.1784 [MH ⁺ ].

Example 7

5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2-hydroxy-1-phenylethyl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (68 mg, 300 μmol; CAN 1613238-32-6) was reacted with (2R)-2-amino-2-phenyl-ethanol (49 mg, 360 μmol; CAN 56613-80-0) in the presence of TBTU and N,N-diisopropylethylamine to obtain the title compound (54 mg, 52%) as a colorless oil, LC-MS: 347.1161 [MH ⁺ ].

Example 8

5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (68 mg, 300 μmol; CAN 1613238-32-6) was reacted with (2S)-2-amino-N,3,3-trimethyl-butyramide (51 mg, 360 μmol; CAN 89226-12-0) in the presence of HATU (137 mg, 360 μmol) and N,N-diisopropylethylamine to obtain the title compound (91 mg, 86%) as a colorless oil, LC-MS: 354.1581 [MH ⁺ ].

Example 9

(-)5-Chloro-4-(cyclopropylmethoxy)-N-[2,2,2-trifluoro-1-pyridin-2-ylethyl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (68 mg, 300 μmol; CAN 1613238-32-6) was reacted with 2,2,2-trifluoro-1-(2-pyridyl)ethylamine (62 mg, 350 μmol; CAN 503173-14-6) in the presence of HATU (137 mg, 360 μmol) and N,N-diisopropylethylamine to obtain (racemic) 5-chloro-4-(cyclopropylmethoxy)-N-[2,2,2-trifluoro-1-pyridin-2-ylethyl]pyridine-2-carboxamide, which was purified by chiral preparative HPLC to provide the title compound (37 mg, 32%) as a colorless oil, LC-MS: 386.0878 [MH ⁺ ].

Example 10

5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2,2,2-trifluoro-1-pyridin-3-ylethyl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (23 mg, 100 μmol; CAN 1613238-32-6) was reacted with (1R)-2,2,2-trifluoro-1-(3-pyridinyl)ethylamine (CAN 1212813-98-3) in the presence of HATU (137 mg, 360 μmol) and N,N-diisopropylethylamine to obtain the title compound (30 mg, 78%) as a colorless oil, LC-MS: 386.0878 [MH ⁺ ].

Example 11

5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (20 mg, 88 μmol; CAN 1613238-32-6) was reacted with (S)-2-amino-N,4-dimethylpentanamide*HCl (21 mg, 114 μmol; CAN 99145-71-8) in the presence of HATU (137 mg, 360 μmol) and N,N-diisopropylethylamine to obtain the title compound (31 mg, quantitative), as a pale yellow oil, LC-MS: 354.1578 [MH ⁺ ].

Example 12

5-Chloro-4-(cyclopropylmethoxy)-N-[(2R)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide

Similar to the procedure described in Example 1d, 5-chloro-4-(cyclopropylmethoxy)pyridine-2-carboxylic acid (20 mg, 88 μmol; CAN 1613238-32-6) was reacted with (R)-2-amino-N,4-dimethylpentanamide*HCl (21 mg, 114 μmol; CAN 99145-71-8) in the presence of HATU (137 mg, 360 μmol) and N,N-diisopropylethylamine to obtain the title compound (31 mg, quantitative), as a pale yellow oil, LC-MS: 354.1573 [MH ⁺ ].

Example 13

5-Cyclopropyl-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]-4-[(3-methyloxetanebut-3-yl)methoxy]pyridine-2-carboxamide

To a solution of 5-cyclopropyl-4-[(3-methyloxetane-3-yl)methoxy]pyridine-2-carboxylic acid (39 mg, 150 μmol; CAN 1613239-78-3) in anhydrous DMF (1.5 mL), 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (46 mg, 165 μmol) and N,N-diisopropylethylamine (68 mg, 92 μL, 525 μmol) were added. The reaction mixture was stirred at ambient temperature for 45 min, and then (2S)-2-amino-N,3,3-trimethyl-butyramide (24 mg, 165 μmol; CAN 89226-12-0) was added. Stirring was continued for 14 h, and the crude mixture was purified by preparative HPLC to obtain the title compound, LC-MS: 390.4 [MH ⁺ ].

Example 14

6-[6-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-4-(cyclopropylmethoxy)pyridin-3-yl]-2-oxa-6-azaspirocyclic[3.3]heptane

Under an argon atmosphere, 2-oxa-6-azaspirocyclic [3.3]heptane hemioxarate (29.5 mg, 102 μmol; CAN 1045709-32-7), Pd(OAc)₂ (3.8 mg, 17 μmol), BINAP (10.6 mg, 17 μmol), and _Cs₂CO₃ (111 mg, 341 μmol) were added to a solution of 3-(5-bromo-4-(cyclopropylmethoxy)pyridin-2-yl) _-5 -tert-butyl-1,2,4-oxadiazole (60 mg, 170 μmol; CAN 1629991-68-9) in anhydrous _toluene (1 mL). The reaction mixture was stirred at 115 °C for 14 hours, filtered through a diatomaceous earth mat, and the filtrate was evaporated to dryness. The crude product was purified by column chromatography (silica gel, 10 g, EtOAc/heptane) to obtain the title compound (15 mg, 24%), LC-MS: 371.0 [MH ⁺ ].

Example 15

(2S)-2-[[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxymethyl]pyrrolidine-1-carboxylic acid tert-butyl ester

To a solution of 5-tert-butyl-3-(4-chloro-5-cyclopropylpyridin-2-yl)-1,2,4-oxadiazole (50 mg, 180 μmol; CAN1629991-73-6) in anhydrous DMF (1 mL), NaH (10.8 mg, 270 μmol) and Boc-L-prolyl (54.3 mg, 270 μmol; CAN 69610-40-8) were added. The reaction mixture was stirred at ambient temperature for 15 min, followed by microwave irradiation at 100 °C for 30 min. Quenching with ice water and purification by preparative HPLC gave the title compound (6 mg, 7%), LC-MS: 443.7 [MH ⁺ ].

Example 16

(3R)-3-[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxypyrrolidine-1-carboxylic acid tert-butyl ester

Similar to the procedure described in Example 15, 5-tert-butyl-3-(4-chloro-5-cyclopropylpyridin-2-yl)-1,2,4-oxadiazole (50 mg, 180 μmol; CAN 1629991-73-6) was reacted with Boc-(R)-3-hydroxypyrrolidine (50.6 mg, 270 μmol; CAN 109431-87-0) in the presence of NaH to obtain the title compound (43 mg, 56%), LC-MS: 429.7 [MH ⁺ ].

Example 17

5-tert-butyl-3-[5-cyclopropyl-4-[(3-methylsulfonylphenyl)methoxy]pyridin-2-yl]-1,2,4-oxadiazole

Similar to the procedure described in Example 15, 5-tert-butyl-3-(4-chloro-5-cyclopropylpyridin-2-yl)-1,2,4-oxadiazole (50 mg, 180 μmol; CAN 1629991-73-6) was reacted with (3-(methylsulfonyl)phenyl)methanol (30 mg, 161 μmol; CAN 220798-39-0) in the presence of NaH to obtain the title compound (8 mg, 10%), LC-MS: 428.6 [MH ⁺ ].

Example 18

N-[1-(azacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl]-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridine-2-carboxamide

a) 1-(1-Diphenylmethylazet-3-yl)acetone

Under an argon atmosphere, a 1.6 M solution of lithium methylcyclobutane-3-carboxamide (1.62 g, 5.22 mmol, CAN 359402-66-7) cooled to -78 °C in anhydrous THF (30 mL) was slowly added (3.75 mL, 6 mmol). The reaction mixture was stirred at -78 °C for 30 min and then at ambient temperature for 14 h. After cooling to -15 °C, a 1.6 M solution of lithium methylcyclobutane-3-carboxamide (1.63 mL, 2.61 mmol) was added. The reaction mixture was stirred at -15 °C for 1 h, water was carefully added, and stirring was continued at 0 °C for ₁₀ min. The reaction medium was diluted with ethyl acetate and washed with a 1 M _NaHCO3 aqueous solution. The layers were separated, the aqueous layer was extracted with ethyl acetate, and the combined organic phases were dried over _Na2SO4 . After filtration, the solvent was removed under reduced pressure. The residue was purified by column chromatography (silica gel, 50 g, ethyl acetate/heptane) to obtain the title compound (1.1 g, 80%), LC-MS: 266.5 [MH ⁺ ].

b)(E)-N-(1-(1-diphenylmethylazet-3-yl)ethylene)-2-methylpropane-2-sulfinamide

Under an argon atmosphere, 2-methylpropane-2-sulfinamide (528 mg, 4.35 mmol; CAN 146374-27-8) and titanium ethoxide (IV) (993 mg, 913 μL, 4.35 mmol) were added to a solution of 1-(1-diphenylmethylazetane-3-yl)acetone (1.1 g, 4.15 mmol) in anhydrous THF (30 mL). The reaction mixture was stirred at 70 °C for 16 h and carefully quenched by adding 5 mL of saturated aqueous NaCl solution. Stirring was continued at ambient temperature for 20 min. The precipitate formed was removed by filtration through a diatomaceous earth mat. The filter cake was washed twice with THF. The filtrate was dried, dissolved in _ethyl acetate, and washed with brine. After drying with _Na₂SO₄ and filtering, the solvent was removed under reduced pressure. The residue was purified by column chromatography (silica gel, 70 g, ethyl acetate/heptane) to obtain the title compound (975 mg, 64%), LC-MS: 369.6 [MH ⁺ ].

c) N-(1-(1-diphenylmethylazonyl-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl)-2-methylpropane-2-sulfinamide

Under an argon atmosphere, a solution of 1.3 M isopropyl magnesium chloride-lithium chloride complex (1.15 mL, 1.49 mmol) in THF (5 mL) cooled to -15 °C was added to a solution of 2-bromo-5-methyl-1,3,4-oxadiazole (243 mg, 1.49 mmol; CAN 864750-58-3) in anhydrous THF (5 mL). The reaction mixture was stirred at -15 °C for 30 min, and then a mixture of 2 M trimethylaluminum (746 μL, 1.49 mmol) in heptane and (E)-N-(1-(1-diphenylmethylazetane-3-yl)ethylene)-2-methylpropane-2-sulfinamide (0.5 g, 1.36 mmol) in anhydrous toluene (8 mL) was added. The mixture was stirred at ambient temperature for 14 h and carefully quenched by dropwise addition of water. Ethyl acetate and 1 M _NaHCO3 aqueous solution were added. The layers were separated. The aqueous layer was extracted with ethyl acetate. The combined organic layers were dried over _{Na₂SO₄ ,} filtered, and the filtrate was dried. The residue was purified by column chromatography (silica gel, 70 g, dichloromethane/methanol) to obtain the title compound (443 mg, 72%), LC-MS: 453.6 [ ^MH⁺ ].

d) 1-(1-Diphenylmethylazacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethylamine

To a solution of N-(1-(1-diphenylmethylazetrazol-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl)-2-methylpropane-2-sulfinamide (433 mg, 957 μmol) in MeOH (5 mL), a solution of 4 M HCl in dioxane (598 μL, 2.39 mmol) was added. The reaction mixture was stirred at ambient temperature for 2 h and concentrated under vacuum. The residue was redissolved in ethyl acetate and washed with 2 M _{Na₂CO₃ aqueous} solution. The aqueous layer was extracted with ethyl acetate. _The combined organic layers were dried over _Na₂SO₄ , filtered, and the filtrate was dried. The residue was purified by column chromatography (silica gel, 20 g, dichloromethane/methanol) to obtain the title compound (123 mg, 37%), LC-MS: 349.6 [ ^MH⁺ ].

e)N-(1-(1-diphenylmethylazacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl)-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridineamide

Similar to the procedure described in Example 1d, 5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridinecarboxylic acid (85 mg, 325 μmol; CAN 1613238-51-9) was reacted with 1-(1-diphenylmethylazacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethylamine (119 mg, 342 μmol) in the presence of TBTU and N,N-diisopropylethylamine to obtain the title compound (100 mg, 52%), LC-MS: 592.6 [MH ⁺ ].

f) N-[1-(azacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl]-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridine-2-carboxamide

Under an argon atmosphere, a solution of N-(1-(1-diphenylmethylazacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl)-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridineamide (100 mg, 169 μmol) in EtOH (1 mL) was added to a solution of N-(1-(1-diphenylmethylazacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl)-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridineamide (100 mg, 169 μmol). The reaction was carried out under a 2.5 bar _H₂ atmosphere and stirred at room temperature for 14 hours. Trifluoroacetic acid (193 mg, 130 μL, 1.69 mmol) and 10% Pd/C (10% w/w, 10 mg, 94 μmol) were added to the mixture. The mixture was stirred at 50 °C under a 2 bar H₂ atmosphere for 3 hours. The mixture was filtered through a diatomaceous earth pad, and the filter cake was washed twice with ethanol. The filtrate was concentrated, and the crude product was immediately purified by preparative HPLC to obtain the title compound (25 mg, 35%) as a white solid, LC-MS: 426.3 [MH ⁺ ].

Example 19

2-[[5-cyclopropyl-4-[(3-methyloxetane-3-yl)methoxy]pyridine-2-carbonyl]amino]-2-ethylbutyrate ethyl ester

Similar to the procedure described in Example 13, 5-cyclopropyl-4-((3-methyloxetane-3-yl)methoxy)pyridinecarboxylic acid (19.5 mg, 74.1 μmol; CAN 1613239-78-3) was reacted with ethyl 2-amino-2-ethylbutyrate hydrochloride (14.5 mg, 74 μmol; CAN 1135219-29-2) in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholino-4-onium chloride and N,N-diisopropylethylamine to give the title compound (26 mg, 86%), LC-MS: 405.7 [MH ⁺ ].

Example 20

5-Chloro-N-[1-Cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-[(2,2-difluoro-1-methylcyclopropyl)methoxy]pyridine-2-carboxamide

a) 4,5-Dichloro-N-(1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl)pyridineamide

A mixture of 4,5-dichloropyridinecarboxylic acid (100 mg, 521 μmol; CAN 73455-13-7), 1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-amine hydrochloride (136 mg, 625 μmol; CAN 1415900-39-8), 2-bromo-1-ethylpyridinium tetrafluoroborate (284 mg, 885 μmol), and N,N-diisopropylethylamine (212 mg, 281 μL) in dioxane (0.8 mL) was stirred at 80 °C for 14 hours, poured into ice/saline solution (1 x 25 mL), and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with ice water/saline solution ( ₂₅ mL), dried over _Na₂SO₄ , and filtered. The filtrate was dried and the residue was purified by column chromatography (silica gel, 10 g, heptane/ethyl acetate) to obtain the title compound (120 mg, 65%) as a colorless liquid, LC-MS: 355.2 [MH ⁺ ].

b) 5-Chloro-N-[1-Cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-[(2,2-difluoro-1-methylcyclopropyl)methoxy]pyridine-2-carboxamide

Potassium tert-butoxide (28 mg, 246 μmol) and potassium benzoate (39.4 mg, 246 μmol) were added to a solution of (2,2-difluoro-1-methylcyclopropyl)methanol (15 mg, 123 μmol; CAN 128230-72-8) and 4,5-dichloro-N-(1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl)pyridineamide (65.5 mg, 184 μmol) in DMF (375 μL). The mixture was heated in a microwave oven at 130 °C for 5 hours, poured into ice/0.1 N HCl (1 x 25 mL), and extracted with EtOAc (2 x 50 mL). The combined extracts were washed with ice/saline (1 x 25 mL), _dried with _Na₂SO₄ , and then dried after filtration. The crude compound was purified by preparative TLC (silica gel, 1.0 mm, hexane/EtOAc 1:1) to give the title compound, LC-MS: 441.2 [MH ⁺ ].

Example 21

4-(benzotriazol-1-yloxy)-N-[1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-5-(trifluoromethyl)pyridine-2-carboxamide

A mixture of 4-chloro-5-(trifluoromethyl)pyridinecarboxylic acid (20 mg, 88.7 μmol; CAN 1211591-26-2), 1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-amine hydrochloride (23.2 mg, 106 μmol; CAN 1415900-39-8), TBTU (48.4 mg, 151 μmol), and N,N-diisopropylethylamine (36.1 mg, 47.8 μL, 279 μmol) in DMF (200 μL) was stirred at ambient temperature for 3 hours, poured into ice/saline/1N HCl (25 mL), and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with saturated aqueous solution of _NaHCO3 (25 mL) and ice/saline ( ₂₅ mL), dried over _Na2SO4 , and filtered. The filtrate was dried and the residue was purified by preparative TLC (silica gel, 2.0 mm, hexane/EtOAc 1:1) to obtain the title compound (27 mg, 63%) as a colorless liquid, LC-MS: 488.2 [MH ⁺ ].

Example 22

N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide

a) N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-4-chloro-5-cyclopropylpyridineamide

Similar to the procedure described in Example 20a, 4-chloro-5-cyclopropylpyridinecarboxylic acid (80 mg, 405 μmol; CAN 1256790-74-5) was reacted with 3-amino-3-cyclopropylbutyramide hydrochloride (145 mg, 486 μmol; CAN for free base: 1534510-01-4) in the presence of 2-bromo-1-ethylpyridinium tetrafluoroborate and N,N-diisopropylethylamine to obtain the title compound (55 mg, 42%) as a colorless liquid, LC-MS: 322.2 [MH ⁺ ].

b) N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide

Potassium tert-butoxide (13.9 mg, 124 μmol) and potassium benzoate (19.9 mg, 124 μmol) were added to a solution of N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-4-chloro-5-cyclopropylpyridineamide (20 mg, 62.2 μmol) and (5-fluoropyridin-2-yl)methanol (9.48 mg, 74.6 μmol; CAN 802325-29-7) in DMF (500 μL). The reaction mixture was heated in a microwave oven to 130 °C for 5 hours, poured into ice/0.1 N HCl (25 mL), and extracted with EtOAc (2 x 50 mL). The combined extracts were washed with ice/saline ( ₂₅ mL), dried over _Na₂SO₄ , and filtered. The filtrate was dried and the residue was purified by preparative TLC (silica gel, 2.0 mm, EtOAc) to obtain the title compound (2 mg, 8%) as a colorless liquid, LC-MS: 413.2 [MH ⁺ ].

Example 23

N-[(2S)-1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-(6-fluoropyridin-3-yl)-5-phenylmethoxypyridin-2-carboxamide

a) Methyl 5-(benzyloxy)-4-bromopyridinecarboxylate

A mixture of methyl 4-bromo-5-hydroxypyridinecarboxylate (200 mg, 862 μmol; CAN 1256836-99-3), potassium carbonate (477 mg, 3.45 mmol), and (chloromethyl)benzene (164 mg, 149 μL, 1.29 mmol; CAN 100-44-7) in DMF (8 mL) was stirred at ambient temperature for 20 h. Stirring was continued at 50 °C for 8 h, and the reaction mixture was then poured into ice water/saline (25 mL) and extracted with EtOAc (2 x 50 mL). The combined extracts were washed with ice water/saline (2 x 25 _mL ), dried over _Na₂SO₄ , and filtered. The filtrate was dried, and the residue was purified by preparative column chromatography (silica gel, 10 g, heptane/EtOAc) to obtain the title compound (155 mg, 56%) as a grayish-white solid, LC-MS: 324.1 [MH ⁺ ].

b) 5-(benzyloxy)-4-bromopyridinecarboxylic acid

A mixture of methyl 5-(benzyloxy)-4-bromopyridinecarboxylate (153 mg, 475 μmol) and lithium hydroxide hydrate (29.9 mg, 712 μmol) in THF (1.5 mL) and water (0.75 mL) was stirred at ambient temperature for 20 hours, poured into ice water/0.1 N HCl aqueous solution (25 mL), and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with ice water/saline ( ₂₅ mL), dried over _Na₂SO₄ , and filtered. The filtrate was dried to obtain the title compound (128 mg, 88%) as a grayish-white solid, LC-MS: 308.1 [ ^MH⁺ ].

c)(S)-5-(benzyloxy)-4-bromo-N-(1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl)pyridineamide

Similar to the procedure described in Example 20a, 5-(benzyloxy)-4-bromopyridinecarboxylic acid (30 mg, 97.4 μmol) was reacted with (S)-1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-amine hydrochloride (25.4 mg, 117 μmol; (S)-enantiomer CAN1415900-39-8) in the presence of 2-bromo-1-ethylpyridinium tetrafluoroborate and N,N-diisopropylethylamine to obtain the title compound (38 mg, 42%) as a colorless liquid, LC-MS: 473.3 [MH ⁺ ].

d)N-[(2S)-1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-(6-fluoropyridin-3-yl)-5-phenylmethoxypyridin-2-carboxamide

Under an argon atmosphere, 1,1'-bis(diphenylphosphino)ferrocene palladium(II) chloride (4.24 mg, 5.2 μmol) was added to a mixture of (S)-5-(benzyloxy)-4-bromo-N-(1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl)pyridine amide (35 mg, 74.3 μmol), 2-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)pyridine (21.5 mg, 96.5 μmol; CAN 444120-95-0) and 2M Cs ₂ CO ₃ aqueous solution (92.8 μL, 186 μmol) in dioxane (700 μL). The mixture was heated in a microwave oven to 120°C for 8 hours, poured into ice/1N HCl, and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with ice/saturated aqueous _NaHCO3 solution (25 mL) and ice water/salt water ( ₂₅ mL), dried over _Na2SO4 , and filtered. The filtrate was dried, and the residue was purified by preparative TLC (silica gel, 2.0 mm, hexane/EtOAc 1:1) to obtain the title compound (20 mg, 55%) as a colorless liquid, LC-MS: 488.4 [MH ⁺ ].

Example 24

Pharmacological testing

The following tests were performed to determine the activity of the compound of formula I:

Radioligand binding assay

The affinity of the compounds of the present invention for cannabinoid receptors was determined using recommended amounts of membrane preparations (PerkinElmer) from human embryonic kidney (HEK) cells expressing human CNR1 or CNR2 receptors, in combination with 1.5 or 2.6 nM [3H]-CP-55,940 (Perkin Elmer) as radioligands. Binding was performed in 0.2 ml of binding buffer (for CB1 receptors: 50 mM Tris, 5 mM _MgCl2 , 2.5 mM EDTA, and 0.5% (wt/vol) fatty acid-free BSA, pH 7.4; and for CB2 receptors: 50 mM Tris, ₅ mM MgCl2, 2.5 mM EGTA, and 0.1% (wt/vol) fatty acid-free BSA, pH 7.4) with shaking at 30 °C for 1 h. The reaction was terminated by rapid filtration through a microfilter plate (UniFilter GF/B filter plate; Packard) coated with 0.5% polyethyleneimine. Nonlinear regression analysis (Activity Base, IDBusiness Solution, Limited) was used to analyze the bound radioactivity for Ki, and the Kd value for [3H]CP55,940 was determined from saturation experiments. The compound of formula (I) showed excellent affinity for the CB2 receptor.

In the above assay (Ki), the compound according to formula (I) exhibits an activity of 10 nM to 10 μM. In the above assay (Ki), a particular compound of formula (I) exhibits an activity of 10 nM to 3 μM. In the above assay (Ki), other particular compounds of formula (I) exhibit an activity of 10 nM to 100 nM.

cAMP assay

CHO cells expressing human CB1 or CB2 receptors were seeded at 50,000 cells/well in DMEM (Invitrogen No. 31331) (supplemented with 1x HT and 10% fetal bovine serum) in black 96-well plates (Corning Costar #3904) with clear flat bottoms 17–24 hours prior to the experiment and incubated in a humidified incubator at 5% _CO2 and 37°C. The growth medium was exchanged with Krebs Ringer bicarbonate buffer containing 1 mM IBMX and incubated at 30°C for 30 min. The compound was added to a final assay volume of 100 μl and incubated at 30°C for 30 min. The cAMP-Nano-TRF detection kit (Roche Diagnostics) was used to terminate the assay by adding 50 μl of lysis reagent (Tris, NaCl, 1.5% Triton X100, 2.5% NP40, ₁₀ % NaN3) and 50 μl of detection solution (20 μM mAb Alexa700-cAMP 1:1, and 48 μM ruthenium-2-AHA-cAMP) and oscillating at room temperature for 2 hours. Time-resolved energy transfer was measured using a TRF reader (Evotec Technologies GmbH) equipped with an ND:YAG laser as the excitation source. The plate was measured twice, with excitation at 355 nm and gate emission at 730 nm (bandwidth 30 nm) or 645 nm (bandwidth 75 nm) with a delay of 100 ns and a gate emission of 100 ns, respectively, for a total exposure time of 10 s. The FRET signal was calculated as follows: FRET = T730 - Alexa730 - P(T645 - B645), where P = Ru730 - B730/Ru645 - B645, where T730 is the test well measured at 730 nm, T645 is the test well measured at 645 nm, and B730 and B645 are buffer controls at 730 nm and 645 nm, respectively. cAMP levels were determined as a function of a standard curve of cAMP ranging from 10 μM to 0.13 nM.

_EC50 values were determined using Activity Base analysis (ID Business Solution, Limited). The _{EC50 values} for a wide range of cannabinoid agonists derived from this assay for the reference compound were consistent with values published in the scientific literature.

In the aforementioned assays, the compounds according to the invention have 5 nM to 10 μM human CB2 EC _50. Specific compounds according to the invention have 5 nM to 1 μM human CB2 EC _50. Other specific compounds according to the invention have 5 nM to 100 nM human CB2 EC _50. In both radioligand and cAMP assays, or in one of these two assays, they all exhibit at least 10-fold selectivity for the human CB1 receptor.

The table below shows the results obtained for representative compounds of the present invention.

The second column presents the relative efficacy (in percent) compared to the reference agonist CP55940, with the value set at +100%, measured in a manner similar to the assay described by Ullmer, C. et al. Functional monoclonal antibodies act as biased agonists by inducing internalization of metabolized glutamate receptor 7. Br. J. Pharmacol. 167, 1448-66 (2012). Negative values indicate that the compound of formula (I) is an inverse agonist.

Example A

Film-coated tablets containing the following ingredients can be prepared using conventional methods:

The active ingredient was sieved and mixed with microcrystalline cellulose, and the mixture was granulated using a solution of polyvinylpyrrolidone in water. The granules were then mixed with sodium starch glycolate and magnesium stearate and pressed to obtain cores of 120 or 350 mg, respectively. The cores were then coated with an aqueous solution/suspension of the aforementioned film-coating agent.

Example B

Capsules containing the following ingredients can be prepared using conventional methods:

<![CDATA[<u>Components</u>]]> <![CDATA[<u>per capsule</u>]]> Compound of formula (I) 25.0mg lactose 150.0mg corn starch 20.0mg talc 5.0mg

The sieved groups were separated and mixed, and then filled into capsule No. 2.

Example C

Injectable solutions may have the following components:

Compound of formula (I) 3.0mg Polyethylene glycol 400 150.0mg Acetic acid Add an appropriate amount to bring the pH to 5.0. Water for injection Add to 1.0ml

Dissolve the active ingredient in a mixture of polyethylene glycol 400 and water for injection (partially). Adjust the pH to 5.0 by adding acetic acid. Adjust the volume to 1.0 ml by adding the remaining water. Filter the solution, dispense the appropriate excess into vials, and sterilize.

Claims (9)

1. A compound, said compound being selected from... 5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide; 4-(4-Chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1R,2S)-2-hydroxycyclohexyl]pyridine-2-carboxamide; 4-(4-Chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1S,2R)-2-hydroxycyclohexyl]pyridine-2-carboxamide; 2-[[4-(4-chlorophenyl)-5-(cyclopropylmethoxy)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester; 2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester; 4-(4-Chlorophenyl)-5-(cyclopropylmethoxy)-N-[(1R,2S)-2-methoxycyclohexyl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2-hydroxy-1-phenylethyl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(1S)-2,2,2-trifluoro-1-pyridin-2-ylethyl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(1R)-2,2,2-trifluoro-1-pyridin-3-ylethyl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide; 5-Chloro-4-(cyclopropylmethoxy)-N-[(2R)-4-methyl-1-(methylamino)-1-oxopent-2-yl]pyridine-2-carboxamide; 5-Cyclopropyl-N-[(2S)-3,3-Dimethyl-1-(methylamino)-1-oxobut-2-yl]-4-[(3-methyloxetanebut-3-yl)methoxy]pyridine-2-carboxamide; 6-[6-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-4-(cyclopropylmethoxy)pyridin-3-yl]-2-oxa-6-azaspirocyclic[3.3]heptane; (2S)-2-[[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxymethyl]pyrrolidine-1-carboxylic acid tert-butyl ester; (3R)-3-[2-(5-tert-butyl-1,2,4-oxadiazol-3-yl)-5-cyclopropylpyridin-4-yl]oxypyrrolidine-1-carboxylic acid tert-butyl ester; 5-tert-butyl-3-[5-cyclopropyl-4-[(3-methylsulfonylphenyl)methoxy]pyridin-2-yl]-1,2,4-oxadiazole; N-[1-(azacyclobut-3-yl)-1-(5-methyl-1,3,4-oxadiazol-2-yl)ethyl]-5-cyclopropyl-4-(2,2,2-trifluoroethoxy)pyridine-2-carboxamide; 5-Chloro-N-[1-Cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-[(2,2-difluoro-1-methylcyclopropyl)methoxy]pyridine-2-carboxamide; 4-(benzotriazol-1-yloxy)-N-[1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-5-(trifluoromethyl)pyridine-2-carboxamide; N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide; and N-[(2S)-1-cyclopropyl-2-(5-methyl-1,2,4-oxadiazol-3-yl)propyl-2-yl]-4-(6-fluoropyridin-3-yl)-5-phenylmethoxypyridine-2-carboxamide. 2. The compound according to claim 1, wherein the compound is selected from... 5-(cyclopropylmethoxy)-4-(2,4-dichlorophenyl)-N-[(2S)-1-hydroxy-4-methylpent-2-yl]pyridine-2-carboxamide; 2-[[5-(cyclopropylmethoxy)-4-(3,4-dichlorophenyl)pyridine-2-carbonyl]amino]-2-ethylbutyrate methyl ester; 5-Chloro-4-(cyclopropylmethoxy)-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]pyridine-2-carboxamide; 5-Cyclopropyl-N-[(2S)-3,3-dimethyl-1-(methylamino)-1-oxobut-2-yl]-4-[(3-methyloxetanebut-3-yl)methoxy]pyridine-2-carboxamide; and N-(4-amino-2-cyclopropyl-4-oxobut-2-yl)-5-cyclopropyl-4-[(5-fluoropyridin-2-yl)methoxy]pyridine-2-carboxamide. 3. The compound according to claim 1 or 2, which is used as a therapeutically active substance. 4. A pharmaceutical composition comprising the compound according to claim 1 or 2 and a therapeutically inert carrier. 5. Use of the compound according to claim 1 or 2 in the preparation of a medicament for the treatment or prevention of pain, asthma, osteoporosis, inflammation, mental illness, tumors, malaria, immune disorders, gastrointestinal disorders, or allergic reactions. 6. Use of the compound according to claim 1 or 2 in the preparation of a medicament for the treatment or prevention of neuropathic pain, encephalitis, arthritis or rheumatoid arthritis. 7. The compound according to claim 1 or 2, for the treatment or prevention of pain, asthma, osteoporosis, inflammation, mental illness, tumors, malaria, immune disorders, gastrointestinal disorders or allergic reactions. 8. The compound according to claim 1 or 2, for the treatment or prevention of neuropathic pain, encephalitis, arthritis or rheumatoid arthritis. 9. The compound according to claim 7, for the treatment or prevention of pain or mental illness.