A solution of phosphorus tribromide (5.0 g) in tetrahydrofuran (10 ml) was dropwise added to a mixture of benzhydryl 7-phenylacetamido-3-hydroxymethyl-3-cephem-4-carboxylate (25.7 g) in tetrahydrofuran (200 ml) at -10° to -5° C. and the mixture was stirred at the same temperature for 15 minutes. The resultant mixture was poured into a mixture of water (250 ml) and ethyl acetate (300 ml). The separated organic layer was washed with brine and dried over magnesium sulfate. The solvent was evaporated to give the oily product. The crude oily product was dissolved in ethyl acetate (250 ml) and triphenylphosphine (21 g) was added. The mixture was stirred at ambient temperature for 3 hours. The precipitate was collected by filtration and washed with ethyl acetate to give (4-benzhydryloxycarbonyl-7-phenylacetamido-3-cephem-3-ylmethyl)triphenyl phosphonium bromide (22.8 g).
