(4-benzhydryloxycarbonyl-7-amino-3-cephem-3-ylmethyl)triphenylphosphonium iodide hydrochloride (5 g) was dissolved in a mixed solution of tetrahydrofuran (35 ml) and 35 ml of aqueous sodium bicarbonate (1.6 g). To the solution was added a solution of 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-ethoxyimino acetylchloride hydrochloride (syn isomer) (2.6 g) in tetrahydrofuran at -3° C. to 3° C., and the solution was stirred for 30 minutes under keeping the pH 6.5 to 7.5 with 20% aqueous potassium carbonate. Ethyl acetate was added to the reaction mixture and the mixture was adjusted to pH 10.0 with 20% aqueous potassium carbonate. The separated organic layer was washed with saturated aqueous sodium chloride, dried over magnesium sulfate and evaporated to give benzhydryl 7-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-ethoxyiminoacetamido]-3-(triphenylphosphoranediylmethyl)-3-cephem-4-carboxylate (syn isomer) (4.5 g).
