[CH3:1][O:2][C:3]([CH:5]1[CH2:9][C:8](=[O:10])[N:7]([C:11]2[CH:16]=[CH:15][C:14]([OH:17])=[CH:13][CH:12]=2)[CH2:6]1)=[O:4].[F:18][C:19]1[CH:26]=[CH:25][C:22]([CH2:23]Br)=[CH:21][CH:20]=1.C(=O)([O-])[O-].[K+].[K+]>CC(=O)CC.C(OCC)(=O)C>[CH3:1][O:2][C:3]([CH:5]1[CH2:9][C:8](=[O:10])[N:7]([C:11]2[CH:12]=[CH:13][C:14]([O:17][CH2:23][C:22]3[CH:25]=[CH:26][C:19]([F:18])=[CH:20][CH:21]=3)=[CH:15][CH:16]=2)[CH2:6]1)=[O:4]
A solution of 5.0 g (21.3 mmol) of (RS)-1-(4-hydroxy-phenyl)-5-oxo-pyrrolidine-3-carboxylic acid methyl ester [Example 2 b)] in 200 ml of 2-butanone is treated with 3.55 ml (27.6 mmol) of 4-fluorobenzyl-bromide and 5.88 g (42.5 mmol) of potassium carbonate and the mixture is stirred at 90° C. for 3 hours. For the working-up, the reaction mixture is diluted with ethyl acetate and extracted with water. The organic phase is separated, dried over sodium sulfate and evaporated under reduced pressure. For purification, the material obtained is chromatographed on silica gel using a 98:2-mixture dichloromethane and methanol as the eluent. There are obtained 7.18 g (98% of theory) of (RS)-1-[4-(4-fluoro-benzyloxy)-phenyl]-5-oxo-pyrrolidine-3-carboxylic acid methyl ester as a white solid. MS: m/e=344 (M+H)+.
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