Diisopropyl Ether → Benzhydryl 7-[2-tert-butoxycarbonylmethoxyimino-2-(2-formamidothiazol-4-yl)-acetamido]-3-vinyl-3-cephem-4-carboxylate

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The activated acid, which was prepared from 2-tert-butoxycarbonylmethoxyimino-2-(2-formamidothiazol-4-yl)acetic acid (syn isomer) (13.8 g), N,N-dimethylformamide (3.66 g) and phosphorus oxychloride (7.7 g) in tetrahydrofuran (80 ml) in a conventional manner, was added to a solution of benzhydryl 7-amino-3-vinyl-3-cephem-4-carboxylate hydrochloride (15 g) and trimethylsilylacetamide (32 g) in ethyl acetate (150 ml) at -20° C. with stirring, and the stirring was continued at the same temperature for half an hour. After addition of water (100 ml), the ethyl acetate layer was separated out, and washed with an aqueous solution of sodium chloride, an aqueous solution of sodium bicarbonate and then an aqueous solution of sodium chloride in turn, followed by drying over anhydrous magnesium sulfate. Removal of the solvent gave an oil, which was pulverized with diisopropyl ether and washed with the same to obtain benzhydryl 7-[2-tert-butoxycarbonylmethoxyimino-2-(2-formamidothiazol-4-yl)acetamido]-3-vinyl-3-cephem-4-carboxylate (syn isomer) (23.1 g), mp 101° C. (dec.).

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