In a mixed solvent consisting of 15 ml of methanol, 6 ml of tetrahydrofuran, 1.5 ml of water and 6 ml of methylene chloride was dissolved 740 mg of (3R,5R)-3-(3-benzylideneamino-2-oxoimidazolidin-1-yl)-6-(3,5-di-tert-butyl-4-hydroxybenzylideneamino)-6-methoxy-3-(p-nitrobenzyloxycarbonyl)-7-oxo-4-thia-1-azabicyclo-[3.2.0]heptane. Thereto was added 240 mg of a Girard reagent (2-hydrazino-N,N,N-trimethyl-2-oxoethanaminium chloride). The mixture was stirred at room temperature for 1 hour. To the reaction mixture were added 30 ml of methylene chloride and 10 ml of water. The resulting mixture was adjusted to pH 7.0 with a saturated aqueous sodium hydrogencarbonate solution. The organic layer was separated, washed with a saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure. The residue was purified by column chromatography (eluant: benzene/ethyl acetate=5/1 to 1/1) to obtain 320 mg (yield: 60.6%) of (3R,5R)-6-amino-3-(3-benzylideneamino-2-oxoimidazolidin-1-yl)-6-methoxy-3-(p-nitrobenzyloxycarbonyl)-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane.
