RS50816B - Synthesis of deoxybiotinyl hexamethylenediamine-dota - Google Patents

Abstract

A process for the synthesis of deoxybiotinyl hexamethylenediamine-DOTA comprising the reaction of biotinyl hexamethylenediamine with tri-t-butyl-DOTA in the presence of benzotriazol-1-yl-oxytri pyrrolidinophosphonium hexafluorophosphate as a condensing agent and a further triethylamine.

Description

SYNTHESIS OF DEOXYBIOTINYL

HEXAMETHYLENEDIAMINE-DOTA

TECHNICAL FIELD

The patent filed here relates to an improved procedure for the synthesis of deoxybiotinyl hexamethylenediamine-DOTA.

STATE OF THE ART

The compound deoxybiotinyl hexamethylenediamine-DOTA is described in international patent application VVO 02066075 entitled Applicant. DOTA is 1,4,7,10-tetraazacyclododecanetetra-acetic acid (1,4,7,1O-tetraazacyclododecane-tetra-acetic acid).

The structural formula of deoxybiotinyl hexamethylenediamine-DOTA is shown here for completeness.

The procedure for synthesizing this product is also described in the same patent application WO 02066075 and is also shown in the example on page 15 of the aforementioned application. The compound disclosed here as ST2210 corresponds to compound 4 of Example VVO 02066075. In particular, the intermediate biotinyl hexamethylenediamine hydrochloride (ST2551 or compound 3 of Example in VVO 02066075) was obtained by preparative chromatography with a yield of 55% and an undefined titer.

The final deoxybiotinyl hexamethylenediamine-DOTA product (ST2210 or compound 4 of example in VVO 02066075) was obtained by condensing ST2551 with DOTA, as illustrated in Scheme 1.

The reaction carried out in this way leads to low synthetic yields (the presence of four equivalents of the unprotected carboxyl functional group in DOTA, involves the formation of various side-products) and purification problems. True, to obtain the final product, it was necessary to use HPLC on a preparative scale with a yield of 20%.

DESCRIPTION OF THE INVENTION

Uscale-in research (increases in a certain ratio, cf. trans.), with the aim of improving the yield in the process and facilitating the purification process, alternative synthetic procedures were examined: The improved synthesis process has the following advantages over the one described earlier: 1. in the coupling or condensation step (in VVO 02066075 described as "step d") using tri-tert-butyl-DOTA, the formation of more condensation products is avoided due to partial reactivity of free carboxyls that occur even when operating under controlled pH conditions; 2. still in the same step, the condensing agent and the base were changed; improved yield was obtained by using benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP-Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate) as a condensing agent and triethylamine (TEA) as a base; 3. biotinyl hexamethylenediamine (ST2251) is used as a free base, showing that the use of dihydrochloride causes an increase in the amount of unwanted products; in particular, the formation of by-products corresponding to the dimer, in which ST2551 reacts with 2 molecules of tri-f-butyl-DOTA, was noticeable;

4. the final step consists of the hydrolysis of three tert-butyl groups in acidic aq

solution, for example, using 3N to 6N HCl in various product ratios, at times of 1 hour and 12 hours, with yields that were between 96% and 98%;

5. removing two rather laborious preparative chromatography steps from

synthetic process;

6. obtaining a product with a titer of 94% to 96%.

Therefore, the subject of this invention is a process for synthesizing deoxybiotinyl hexamethylenediamine-DOTA, which includes the reaction of biotinyl hexamethylene diamine with tri-f-butyl-DOTA in the presence of benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate, as a condensing agent, and triethylamine, as a base.

The process of the present invention therefore includes a step after the condensation step, which is hydrolysis at acidic pH.

The condensation is preferably carried out in an organic solvent. More preferably, this solvent is dichloromethane.

Of those examined, the best developed synthetic procedure is the one involving the steps shown in Diagram 2.

In addition, the invention is illustrated with Examples, which are in no way limiting the invention itself.

EXAMPLES (for compound numbers, see Diagram 2)

Procedures

The performed tests were monitored using an analytical HPLC system connected to a diode type detector and an electrospray mass spectrometer. The developed analytical procedure includes the use of an ACE C-18 analytical column (150 x 4.60 mm, 5^), a flow rate of 1.0 mL/min and a linear elution gradient of 5-95% B in 20 min (A = H20 + 0.1% TFA; B = AcCN + 0.1% TFA) or from 10-90% B in 20 min or, alternatively, 10% isocratic solution B in 6 min followed by a gradient of 10-90% B in 20 min. For the final product ST2210, the process of working in isocratic solution B at 15% for 40 min is used. The range of wavelengths tested by the detector is 205-400 nm.

Rapid monitoring by TLC involves using eluent mixtures OEt acid type : isopropanol : 30%NH3 or DCM : isopropanol : 30%NH3 (4:5:1) with detection of resolved products (not UV visible) using J2 or phosphomolybdenum reagent.

Production of biotinyl hexamethylenediamine (ST2551) as a free base (2.)

Product ST2551 [(1), 91% purity, 400 mg, 1.0 mmol) was dissolved in water (20 mL) and the solution was placed in a separatory funnel; 2M NaOH solution (20 mL) was added and the precipitated product was extracted with DCM (40 mL) three times. The combined organic phases were dehydrated with anhydrous Na 2 SO 4 and evaporated under reduced pressure. Product (2) was obtained as a white solid (290 mg, yield = 98%).<1>H-NMR(200 MHz, CDCl3) 6 (ppm): 1.25-2.05 [m, 16H, CH(CH2)4i NHCH2(CH2)4)]; 2.50-3.30 (m, 9H, 2 x HCHS and CHS and 3 x CH2N); 4.32 (m, 1 H, CHCHNH); 4.51 (m, 1 H, CHCHNH); 5.77 (s, 1H, CONH; 6.05 (s, 1H, CONH).

ES-MS m/z: 329.5 [M+H]<+>.

Synthesis of deoxybiotinyl hexamethylenediamine - tert - butyl-DOTA (4).

To a solution of tri-tert-butyl-DOTA [(3), 524 mg, 0.915 mmol, 1 eq], PvBOP (714 mg, 1.37 mmol, 1.5 eq), and triethylamine (166 (xL, 1.19 mmol, 1.3 eq) in DCM (5 mL), allowed to stir at room temperature for 10 min, was added dropwise a solution of of ST2551-free base [(2), 300 mg, 0.915 mmol, 1 eq) in DCM (5 mL), which was obtained by heating the mixture to 40°C for 5 min. It was allowed to react at room temperature for 3 hours while monitoring the completion of the reaction by TLC and LC-MS, according to the procedures above.

At the end of the reaction, the solvent was evaporated under reduced pressure, the residue was dissolved in DCM and washed twice with 1M NaOH. The organic phase was dehydrated over Na 2 SO 4 and evaporated under vacuum. The residue obtained in this way was subjected to chromatography on a silica gel column (weight ratio crude product: silica is 1:30) using as an elution system a mixture of DCM: isopropanol 5:4 to which an increasing concentration of 30% aqueous NH3 (from 0.2 to 1) is added. The column was loaded with an initial mixture of DCM : isopropanol : NH 3 (5:4:0.2) and the process was continued with a gradient of NH 3 . The eluting mixture usually becomes homogeneous after shaking; only in the final phase of the elution, with NH3=1 can it be shown that it is necessary to add isopropanol to improve the mixing and, in this case, using the volumetric ratio (4:5:1) (DCM:isopropanol:NH3). A slightly yellow oily product was obtained which tends to produce a foamy solid under vacuum [(4), 600 mg, yield=74%).

<1>H-NMR (300 MHz, DMSO-d6, T=50°C) δ (ppm): 1.16-1.70 [m, 43H, CH(CH2)4 and NHCH2(CH2)4 and 9 x CH3); 2.40-3.32 (m, 34H, 2 x HCHS and CHS and 3 x CH2N, 8 x DOTA-ring CH2 and CHS and 4 x DOTA CH2CO and NH amine); 4.13 (m, 1 H, CHCHNH); 4.29 (m, 1 H, CHCHNH); 6.18 (s, 1H, NH of biotin); 6.21 (s, 1 H, NH of biotin); 8.10 (t, 1 H, NH amide).

<1>C-NMR (75 MHz, DMSO-d6) δ (ppm): 27.22; 27.35; 27.56; 28.50; 28.61; 29.04; 29.23; 30.14; 30.25; 30.39; 39.14; 40.42; 50.07; 52.59; 52.82; 53.24; 54.72; 56.14; 56.92; 57.38; 59.31; 60.05; 61.90; 80.75; 163.34; 170.98; 171.25.

ES-MS m/z: 883.4 [M+H]<+>.

Synthesis of deoxybiotinyl hexamethylenediamine -DOTA [ST2210, (5)].

A solution of (4) (210 mg, 0.238 mmol) in 6N HCl [1 mL, 20% w/v solution of (4)] was allowed to stir at room temperature for 1 hour. The mixture was then evaporated under reduced pressure, and the residue was dissolved in H 2 O (resp. 1:50 w/v) and the solution was subjected to lyophilization. A white solid was obtained (205 mg, 96 %).

<1>H-NMR (200 MHz, DMSO-d6) δ (ppm): 1.30-1.77 [m, 16H, CH(CH2)4i NHCH2(CH2)4]; 2.59 (d, 1H, HCHS); 2.77-2.88 (m, 7H, HCHS and 3 x CH2N); 2.98-3.70 (m, 25H, 8 x DOTA-ring CH 2 and CHS and 4 x DOTA CH 2 CO); 4.15 (m, 1 H, CHCHNH); 4.31 (m, 1 H, CHCHNH); 7.58 (br s, 2H, 2 x NH biotin); 8.86 (t, 1 H, NH amide); 9.19 (number s, 2H, NH2<+>).

"C-NMR (75 MHz, DMSO-d6) 6 (ppm): 25.77; 25.85; 26.32; 26.53; 26.70; 28 74; 29.16; 47.08; 47.16; 48.54; 49.00; 51.35; 53.13; 54.51; 56.90; 165.90

ES-MS m/z: 715.4 [M+H]+.

Claims (4)

1. Method for synthesizing deoxybiotinyl hexamethylenediamine-DOTA, which includes the reaction of biotinyl hexamethylenediamine with tri-f-butyl-DOTA in the presence of benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate, as a condensing agent, and triethylamine, as a base. 2. A process as in claim 1, wherein biotinyl hexamethylenediamine is reacted with tri-f-butyl-DOTA in an organic solvent. 3. A process, as in claim 2, wherein the organic solvent is dichloromethane. 4. A process, as in any of the preceding claims, which includes the subsequent step of hydrolysis in an aqueous medium with an acidic pH.