To a solution of tert-butyl 7β-amino-3-methyl-3-cephem-4-carboxylate (1.35 g, 5.00 mmol) in methylene chloride (30 ml) was added dropwise under ice-cooling butyl chloral (2,2,3-trichlorobutanal) (0.63 ml, 5.0 mmol). The reaction mixture was stirred at room temperature for 10 minutes, was allowed to cool to -20° C., N,N-dimethylaniline (3 ml) was added thereto and then thionyl chloride (0.5 ml) was added dropwise. After stirring under ice-cooling for 1.5 hours, the reaction mixture was poured into ice-water (40 ml), extracted with methylene chloride (30 ml, twice). The organic layer was washed successively with an ice-cooled saturated aqueous solution of potassium hydrogen sulfate (30 ml, twice), ice-water (30 ml), an ice-cooled saturated aqueous solution of sodium hydrogen carbonate (30 ml) and ice-water (30 ml) and then dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure to give 2.13 g (100%) of the title compound as a pale yellow foamy substance.
