[Si]([N:8]1[CH:11]([CH2:12][C:13](=[O:25])[CH2:14][C:15]([O:17][CH2:18][C:19]2[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=2)=[O:16])[CH:10]([N:26]=[N+:27]=[N-:28])[C:9]1=[O:29])(C(C)(C)C)(C)C.Cl>CO.O>[N:26]([CH:10]1[CH:11]([CH2:12][C:13](=[O:25])[CH2:14][C:15]([O:17][CH2:18][C:19]2[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=2)=[O:16])[NH:8][C:9]1=[O:29])=[N+:27]=[N-:28]A solution of N-(t-butyldimethylsilyl)-3-azido-4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one (1.0 g) in methanol (10 ml) is treated with conc. hydrochloric acid (0.1 ml) and left at room temperature for 2 hr. The solution is diluted with water and extracted with ethyl acetate. The extracts are washed with 5% sodium bicarbonate solution and brine, dried, and evaporated under vacuum. The residue is chromatographed on silica gel to give 3-azido-4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one.
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