Trifluoroacetic acid → 7-[2-(2-Formamidothiazol-4-yl)-2-carboxymethoxyiminoacetamido]-3-cephem-4-carboxylic acid

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A mixture of 7-[2-(2-formamidothiazol-4-yl)-2-(tert-butoxycarbonylmethoxyimino)acetamido]-3-cephem-4-carboxylic acid (syn isomer, 2.8 g.), anisole (2.8 ml.) and trifluoroacetic acid (11.2 ml.) was stirred at room temperature for an hour. Ethyl acetate and water were added to the resultant solution and adjusted to pH 7.0 with sodium bicarbonate. The aqueous layer was separated, and the ethyl acetate layer was extracted with water. The aqueous extracts were combined, washed with ethyl acetate and diethyl ether in turn, and then adjusted to pH 2.0 with 10% hydrochloric acid under ice cooling. The precipitates were collected by filtration, washed with water and dried to give 7-[2-(2-formamidothiazol-4-yl)-2-carboxymethoxyiminoacetamido]-3-cephem-4-carboxylic acid (syn isomer, 1.43 g.).

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