[C:1]([O:5][C:6]([N:8]1[CH2:12][C:11](=[O:13])[CH:10]([S:14]([C:17]2[CH:22]=[CH:21][C:20]([O:23][CH2:24][C:25]3[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=3)=[CH:19][CH:18]=2)(=[O:16])=[O:15])[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[BH4-].[Na+].Cl>CO>[C:1]([O:5][C:6]([N:8]1[CH2:12][CH:11]([OH:13])[CH:10]([S:14]([C:17]2[CH:22]=[CH:21][C:20]([O:23][CH2:24][C:25]3[CH:30]=[CH:29][CH:28]=[CH:27][CH:26]=3)=[CH:19][CH:18]=2)(=[O:16])=[O:15])[CH2:9]1)=[O:7])([CH3:4])([CH3:2])[CH3:3](RS)-3-(4-Benzyloxy-benzenesulfonyl)-4-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (13.4 mg, 0.031 mmol) was dissolved in MeOH (0.5 ml), cooled to 0° C. and treated with NaBH4 (1.64 mg, 0.043 mmol). After 0.5 hour stirring at 0° C., the reaction mixture was acidified to pH 1 with 1N HCl. The aqueous phase was extracted with CH2Cl2. The combined organic phases were washed with H2O, dried over Na2SO4, filtered and the solvent was evaporated to provide (3RS,4SR)-3-(4-benzyloxy-benzenesulfonyl)-4-hydroxy-pyrrolidine-1-carboxylic acid tert-butyl ester (12.3 mg, 92%) as a white solid, MS: m/e=434.4 (M+H+).
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