[CH3:1][C:2]([O:4][CH2:5][C:6]1[CH2:15][S:14][C@@H:9]2[C@H:10]([NH2:13])[C:11](=[O:12])[N:8]2[C:7]=1[C:16]([OH:18])=[O:17])=[O:3].[CH2:19]=[C:20]1[O:24][C:22](=[O:23])[CH2:21]1>[OH-].[Na+].C(OCC)(=O)C>[C:2]([O:4][CH2:5][C:6]1[CH2:15][S:14][C@@H:9]2[CH:10]([NH:13][C:22](=[O:23])[CH2:21][C:20](=[O:24])[CH3:19])[C:11](=[O:12])[N:8]2[C:7]=1[C:16]([OH:18])=[O:17])(=[O:3])[CH3:1]5.44 g of 7-aminocephalosporanic acid were dissolved in 20 ml of a 1N aqueous solution of sodium hydroxide, and 1.68 g of diketene were added, with ice-cooling, to the resulting solution. The mixture was stirred at the same temperature for 1 hour, after which it was diluted with 20 ml of ethyl acetate and then acidified. The mixture was extracted twice with ethyl acetate and the combined extracts were washed with an aqueous solution of sodium chloride, dehydrated over anhydrous magnesium sulphate and then concentrated by evaporation under reduced pressure, giving 4.4 g of the title compound as crystals melting at 150° C. (with decomposition).
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