A solution of 25 mg (0.07 mmol) of (RS)-4-amino-1-[4-(3-fluoro-benzyloxy)-phenyl]-pyrrolidin-2-one hydrochloride in 1 ml of dichloromethane is treated with 22 μl (0.16 mmol) of triethylamine and cooled to 0° C. To this solution, 6 μl (0.08 mmol) of acetylchloride are added and stirring at 0° C. is continued for 30 min. For the working-up, the reaction mixture is treated with 2 ml of ammonium hydroxide solution, the organic phase separated, thereafter dried over sodium sulfate and evaporated under reduced pressure. For purification, the material obtained is chromatographed on silica gel using a 95:5 mixture of dichloromethane and methanol as the eluent. There are obtained 20 mg (78% of theory) of (RS)-N-{1-[4-(3-fluoro-benzyloxy)-phenyl]-5-oxo-pyrrolidin-3-yl}-acetamide as a white solid. MS: m/e=343 (M+H)+.
