(Z)-2-(2-tritylamino-4-thiazolyl)-2-[(diphenylmethyloxycarbonyl)(3-thienyl)methyl]oxyiminoacetic acid (1.90 g, 2.58 mmol) and phosphorus pentoxide (0.564 g, 2.71 mmol) were added to dichloromethane (11 ml) under ice-cooling, and then the resulting mixture was stirred for 30 min. Thus obtained solution was added at -60° C. to the solution of 4-methoxybenzyl 7-amino-3-chloromethyl-3-cephem-4-carboxylate (1.046 g, 2.58 mmol) and pyridine (1.04 ml, 12.9 mmol) in dichloromethane (30 ml) at -40° C. The reaction solution was allowed to -20° C. over 40 min. The reaction solution was cooled to -40° C., and 1N hydrochloric acid (12.9 ml) was added thereto. Water was added to the reaction solution, the solution was extracted with dichloromethane (×3), the organic layer was washed with a saturated saline and dried over anhydrous magnesium sulfate, and then the solvent was evaporated to give a caramel (3.50 g). The caramel was subjected to silica gel column chromatography eluting with hexane-ethyl acetate to obtain (4-methoxybenzyl) 7β-[(Z)-2-(2-tritylamino-4-thiazolyl)-2-[[(R S)-(diphenylmethyloxycarbonyl)(3-thienyl)methoxy]imino]acetamido]-3-cloromethyl-3-cephem-4-carboxylate (2.62 g).
