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Under nitrogen atmosphere, the mixture of 440 mg of sodium hydrosulfide and 1.3 ml of diisopropylethylamine in DMF (10 ml) was added to a solution of diphenylmethyl 7β-formamido-3-methanesulfonyloxy-3-cephem-4-carboxylate (2.44 g) in DMF (15 ml) with dry ice-tetrachloromethane cooling. Stirring was continued for 30 minutes, 918 mg of 4-chloromethylpyrazole hydrochloride and 1.04 ml of diisopropylethylamine was added successively to the solution. The whole mixture was stirred for 1 hour, and then poured into a mixture of water and ethyl acetate. Organic layer was separated, and washed with diluted hydrochloric acid and brine, successively, and dried over magnesium sulfate. After evaporation of the solvent, the residue was purified on silica gel (eluent: dichloromethane-acetone) to afford diphenylmethyl 7β-formamido-3-[(pyrazol-4-yl)-methylthio]-3-cephem-4-carboxylate (2.96 g).

1. stirringThe whole mixture was stirred for 1 hour
2. customOrganic layer was separated
3. washwashed with diluted hydrochloric acid and brine
4. dry with materialsuccessively, and dried over magnesium sulfate
5. customAfter evaporation of the solvent
6. customthe residue was purified on silica gel (eluent: dichloromethane-acetone)