4-(5-ethyl-3,3-dimethyl-2,4-dioxopyrrolidin-1-yl)-2-(trifluoromethyl)benzonitrile 、 L-SELECTRIDE tetrahydrofuran 以in the same manner as in Example 5, the title compound was obtained as a colorless solid (yield: 76 mg, 63%)的产率得到rac-4-[(4R,5R)-5-ethyl-4-hydroxy-3,3-dimethyl-2-oxopyrrolidin-1-yl]-2-(trifluoromethyl)benzonitrile