[Br:1][C:2]1[C:7]2[C:8]([C:16]3[CH:21]=[CH:20][CH:19]=[CH:18][C:17]=3[Cl:22])=[N:9][C@@H:10]([CH3:15])[C:11](=[O:14])[N:12]([CH3:13])[C:6]=2[CH:5]=[CH:4][C:3]=1[NH:23][C:24]([NH:26][CH2:27][CH:28]1[CH2:32][O:31]C(C)(C)[O:29]1)=[O:25].Cl>C(O)C>[Br:1][C:2]1[C:7]2[C:8]([C:16]3[CH:21]=[CH:20][CH:19]=[CH:18][C:17]=3[Cl:22])=[N:9][C@@H:10]([CH3:15])[C:11](=[O:14])[N:12]([CH3:13])[C:6]=2[CH:5]=[CH:4][C:3]=1[NH:23][C:24]([NH:26][CH2:27][CH:28]([OH:29])[CH2:32][OH:31])=[O:25]A solution of 1-[(S)-6-bromo-5-(o-chlorophenyl)-2,3-dihydro-1,3-dimethyl-2-oxo-1H-1,4-benzodiazepin-7-yl]-3-[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl]urea in ethanol is stirred at room temperature for 5 hours with 1N hydrochloric acid. The mixture is extracted with ethyl acetate, washed with water, dried over sodium sulphate and evaporated. The residue is chromatographed on silica gel while eluting with ethyl acetate/methanol (95:5). After recrystallization from methanol/ether, there is obtained 1-[(S)-6-bromo-5-(o-chlorophenyl)-2,3-dihydro-1,3-dimethyl-2-oxo-1H-1,4-benzodiazepin-7-yl]-3-(2,3-dihydroxypropyl)urea of melting point 175° (decomposition).
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