In a manner similar to the method described in Example 100b, [4-methoxy-3,3-dimethyl-but-(E)-ylideneamino]-acetic acid tert-butyl ester prepared in Example 110a (3.8 mmol) was reacted with (Z)-3-(3-chloro-2-fluoro-phenyl)-2-(4-chloro-2-fluoro-phenyl)-acrylonitrile (0.94 g, 3 mmol) prepared in Example 52a, AgF (0.58 g, 4.6 mmol), and triethylamine (1.06 mL, 7.6 mmol) in dichloromethane (100 mL) at room temperature for 18 h, followed by the reaction with DBU (3.6 ml) in tert-butanol (20 mL) at 100° C. for 2 h to give rac-(2R,3S,4R,5S)-3-(3-chloro-2-fluoro-phenyl)-4-(4-chloro-2-fluoro-phenyl)-4-cyano-5-(3-methoxy-2,2-dimethyl-propyl)-pyrrolidine-2-carboxylic acid tert-butyl ester as a light yellow solid (1 g, 59%).
