benzyl (2S)-2-t-butoxycarbonylamino-4-(3-cyanophenoxy)butanoate 、 benzyl (2S)-2-(4-dimethylcarbamoylbenzoylamino)-4-(3-cyanophenoxy)butyrate 以obtained in the same manner as in step 2 in Example 91 from 4-dimethylcarbamoylbenzoic acid as the starting material的产率得到4-(N,N-二甲氨基羰基)苯甲酸