Br[CH2:2][C:3]([C@@H:5]1[CH2:9][C@@H:8]([O:10][S:11]([CH3:14])(=[O:13])=[O:12])[CH2:7][N:6]1[C:15]([O:17][CH2:18][C:19]1[CH:24]=[CH:23][C:22]([N+:25]([O-:27])=[O:26])=[CH:21][CH:20]=1)=[O:16])=O.[CH3:28][O:29][CH:30]([O:34][CH3:35])[C:31]([NH2:33])=[S:32].C(OCC)(=O)C>CN(C)C(=O)C.ClCCl>[CH3:28][O:29][CH:30]([O:34][CH3:35])[C:31]1[S:32][CH:2]=[C:3]([C@@H:5]2[CH2:9][C@@H:8]([O:10][S:11]([CH3:14])(=[O:13])=[O:12])[CH2:7][N:6]2[C:15]([O:17][CH2:18][C:19]2[CH:24]=[CH:23][C:22]([N+:25]([O-:27])=[O:26])=[CH:21][CH:20]=2)=[O:16])[N:33]=1To a solution of (2S, 4R)-2-bromoacetyl-4-methanesulfonyloxy-1- (4-nitrobenzyloxycarbonyl)pyrrolidine (4.0 g) in a mixture of N,N-dimethylacetamide (10 ml) and dichloromethane (5 ml) was added 2,2-dimethoxythioacetamide (1.28 g) at room temperature. After stirring at room temperature for 12 hours, the mixture was poured into ethyl acetate. The organic layer was washed with water, saturated sodium bicarbonate and brine successively, dried over magnesium sulfate, and evaporated. The obtained oil was subjected to a column chromatography on silica gel and eluted with a mixture of dichloromethane and acetone (20:1, V/V) to give (2S, 4R)-2-[2-(dimethoxymethyl)thiazol-4-yl]-4-methanesulfonyloxy-1- (4-nitrobenzyloxycarbonyl)pyrrolidine (2.6 g).
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