To a solution of rac-(2S,3R,4S)-4-(3-chloro-2-fluoro-phenyl)-3-(4-chloro-2-fluoro-phenyl)-2-(2,2-dimethyl-propyl)-pyrrolidine-3-carbonitrile prepared in Example 3 (0.44 g, 1.04 mmol) in dichloromethane (5 mL) was added 4-isocyanato-benzoic acid ethyl ester (Aldrich, 0.22 g, 1.14 mmol) and triethylamine (0.22 mL, 1.56 mmol). The reaction mixture was stirred at room temperature for 30 min. Water was added, the mixture was partitioned between ethyl acetate and water. The organic layer was separated, washed with water, brine, dried over MgSO4, and concentrated. The residue was purified by chromatography (25% EtOAc in hexanes) to give rac-4-{[(2S,3R,4S)-4-(3-chloro-2-fluoro-phenyl)-3-(4-chloro-2-fluoro-phenyl)-3-cyano-2-(2,2-dimethyl-propyl)-pyrrolidine-1-carbonyl]-amino}-benzoic acid ethyl ester as a white solid (0.59 g, 92%)
