Zavolosotine (Compound 1) is an orally active agonist for somatostatin receptor type 5 (SST5) with EC50 <1 nM. Zavolosotine inhibits insulin and glucagon secretion, increases levels of glucagon in blood in rat model.
Example 4. 4-[(3S)-3-aminopyrrolidin-1-yl]-6-cyano-5-(3,5-difluorophenyl)-N-[(2S)-1,1,1-trifluoropropan-2-yl]pyridine-3-carboxamide (Compound 1-71)
Step 4-1, preparation of tert-butyl (S)-(1-(2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate: to a DMF (70 mL) solution was added 4,6-dichloronicotinaldehyde (6.8 g, 1.0 Eq, 39 mmol), tert-butyl (S)-pyrrolidin-3-ylcarbamate (7.6 g, 1.1 Eq, 41 mmol) and TEA (16 mL, 3.1 Eq, 120 mmol). The resulting mixture was stirred at 50° C. for 4 hours. The reaction crude was quenched with water (100 mL) and extracted with ethyl acetate (3×40 mL). The organic layers were combined, washed with brine, dried and concentrated under vacuum. The remaining residue was purified by silica gel chromatography eluting with ethyl acetate/petroleum ether (1/3) to afford tert-butyl (S)-(1-(2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (5.3 g, 42%) as a yellow solid. MS (M+H) +=326.2.
Step 4-2, preparation of tert-butyl (S)-(1-(3-bromo-2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate: to an AcOH (60 mL) solution of tert-butyl (S)-(1-(2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (5.3 g, 1.0 Eq, 16 mmol) was added NBS (3.1 g, 1.1 Eq, 17 mmol) at 10° C. The resulting mixture was stirred at the same temperature for 1 hour. The reaction mixture was quenched with saturated NaHCO 4 and extracted with ethyl acetate (3×40 mL). The organic layers were combined, washed with brine, dried and concentrated under vacuum. The remaining residue was purified by silica gel chromatography eluting with ethyl acetate/petroleum ether (1/4) to afford tert-butyl (S)-(1-(3-bromo-2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (3.5 g, 53%) as a yellow solid. MS (M+H) +=404.1, 406.1.
Step 4-3, preparation of tert-butyl (S)-(1-(2-chloro-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate: to a mixture of tert-butyl (S)-(1-(3-bromo-2-chloro-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (3.5 g, 1.0 Eq, 8.6 mmol), (3,5-difluorophenyl)boronic acid (0.88 Eq, 7.6 mmol, 1.2 g), Pd(DtBPF)Cl 2 (300 mg, 0.05 Eq, 0.46 mmol) and potassium phosphate (5.4 g, 2.9 Eq, 25 mmol) was added Toluene (140 mL) and water (14 mL) under atmospheric nitrogen. The resulting mixture was stirred at 40° C. for 2 hours. The reaction crude was concentrated under reduced pressure and the remaining residue was purified by silica gel column chromatography eluting with petroleum ether/EtOAc (3:1) to afford tert-butyl (S)-(1-(2-chloro-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (2.7 g, 71%) as a yellow solid. MS (M+H) +=438.0, 440.0.
Step 4-4, preparation of tert-butyl (S)-(1-(2-cyano-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate: to a mixture of tert-butyl (S)-(1-(2-chloro-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (2.7 g, 1.0 Eq, 6.2 mmol), Pd 2(dba) 3.CHCl 3 (310 mg, 0.05 Eq, 0.31 mmol), Zn(CN) 2 (1.4 g, 1.9 Eq, 12 mmol) and (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) (720 mg, 0.20 Eq, 1.24 mmol) was added DMF (30 mL) under atmospheric nitrogen. The resulting mixture was heated under microwave radiation conditions at 135° C. for 1 hour. The reaction crude was quenched with water (100 mL) and extracted with EtOAc (3×40 mL). Organic layers were combined, washed with brine, dried over anhydrous Na 2SO 4, filtered and concentrated under vacuum. The remaining residue was purified by silica gel chromatography eluting with petroleum ether/EtOAc (1:1) to afford tert-butyl (S)-(1-(2-cyano-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (2.2 g, 83%) as a yellow solid. MS (M+H) +=429.2.
Step 4-5, preparation of (S)-4-(3-((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-6-cyano-5-(3,5-difluorophenyl)nicotinic acid: to a tert-butyl alcohol solution (20 mL) of (S)-(1-(2-cyano-3-(3,5-difluorophenyl)-5-formylpyridin-4-yl)pyrrolidin-3-yl)carbamate (2.4 g, 1.0 Eq, 5.1 mmol) was added sodium dihydrogen phosphate (2.4 g, 3.0 Eq, 15 mmol) 2-methylbut-2-ene (11.0 g, 31 Eq, 157 mmol), sodium chlorite (1.0 g, 2.2 Eq, 11 mmol) and water (6.6 mL). The resulting mixture was stirred at ambient temperature for 1 hour. The reaction mixture was quenched with saturated NaHSO 4 (50 mL) and extracted with ethyl acetate (3×40 mL). The organic layers were combined, washed with brine, dried and concentrated under vacuum to afford (S)-4-(3-((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-6-cyano-5-(3,5-difluorophenyl)nicotinic acid (2.0 g, 88%) as a yellow solid. This material was used for next step without purification. MS (M+H) +=445.2.
Step 4-6, preparation of tert-butyl ((S)-1-(2-cyano-3-(3,5-difluorophenyl)-5-(((S)-1,1,1-trifluoropropan-2-yl)carbamoyl)pyridin-4-yl)pyrrolidin-3-yl)carbamate: to a DMF solution (2.0 mL) of (S)-4-(3-((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-6-cyano-5-(3,5-difluorophenyl)nicotinic acid (70 mg, 1.0 Eq, 0.16 mmol) was added (S)-1,1,1-trifluoropropan-2-amine hydrochloride (35 mg, 1.5 Eq, 0.23 mmol), N-ethyl-N-isopropylpropan-2-amine (4.4 Eq, 0.70 mmol, 0.12 mL) and HATU (60 mg, 1.0 Eq, 0.16 mmol). The resulting mixture was stirred at ambient temperature for 2 hours. The reaction crude was purified by Prep-HPLC using the following conditions: SunFire Prep C18 OBD Column, 19*150 mm 5 μm; mobile phase, Water (0.1% FA) and ACN (24.0% ACN up to 46.0% in 7 min); Total flow rate, 20 mL/min; Detector, UV 220 nm. This resulted in tert-butyl ((S)-1-(2-cyano-3-(3,5-difluorophenyl)-5-(((S)-1,1,1-trifluoropropan-2-yl)carbamoyl)pyridin-4-yl)pyrrolidin-3-yl)carbamate (45 mg, 53%) as a light yellow solid. MS (M+H) +=540.3.
Step 4-7, preparation of 4-((S)-3-aminopyrrolidin-1-yl)-6-cyano-5-(3,5-difluorophenyl)-N—((S)-1,1,1-trifluoropropan-2-yl)nicotinamide: to a DCM solution (2.0 mL) of tert-butyl ((S)-1-(2-cyano-3-(3,5-difluorophenyl)-5-(((S)-1,1,1-trifluoropropan-2-yl)carbamoyl)pyridin-4-yl)pyrrolidin-3-yl)carbamate (45 mg, 1.0 Eq, 0.083 mmol) was added TFA (1.0 mL). The resulting mixture was stirred at ambient temperature for 2 hours. The reaction solution was concentrated and freeze-dried under vacuum to afford the TFA salt of 4-((S)-3-aminopyrrolidin-1-yl)-6-cyano-5-(3,5-difluorophenyl)-N—((S)-1,1,1-trifluoropropan-2-yl)nicotinamide bis(2,2,2-trifluoroacetate) (40.2 mg, 72%) as a light yellow solid. MS (M+H) +=440.2.
