2,6-difluoro-4-(3,3,5-trimethyl-2,4-dioxopyrrolidin-1-yl)benzonitrile 、 L-SELECTRIDE tetrahydrofuran 以in the same manner as in Example 5, the title compound was obtained as a colorless solid (yield: 67 mg, 67%)的产率得到Rac-2,6-difluoro-4-[(4r,5r)-4-hydroxy-3,3,5-trimethyl-2-oxopyrrolidin-1-yl]benzonitrile