To a solution of chiral (2R,3S,4R,5S)-3-(3-chloro-2-fluoro-phenyl)-4-(4-chloro-2-fluoro-phenyl)-4-cyano-5-(2,2-dimethyl-propyl)-pyrrolidine-2-carboxylic acid (80.6 mg, 0.172 mmol) in dichloromethane (3 ml) were added DIPEA (89.0 mg, 0.685 mmol) and DIPHENYLPHOSPHINIC CHLORIDE (106 mg, 0.437 mmol). The mixture was stirred for 20 mins under argon before methyl 3-(4-aminophenyl)propanoate (33.4 mg, 0.186 mmol) was added. After 2 hrs, the reaction mixture was diluted with dichloromethane, washed with sat. NaHCO3, water and brine. After drying over Na2SO4 the crude material was purified by silica gel chromatography with ethyl acetate and n-hexanes to give chiral methyl 3-(4-((2R,3S,4R,5S)-3-(3-chloro-2-fluorophenyl)-4-(4-chloro-2-fluorophenyl)-4-cyano-5-neopentylpyrrolidine-2-carboxamido)phenyl)propanoate (104.2 mg, 96%) as a white solid. MS (ES+) m/z Calcd: [(M+H)+]: 628.19. found: 628.1.
