To a solution of 3-acetylthio-1-[4-(N-cyanomethyl-N-isopropyl-carbamoyl)-1,3-thiazol-2-yl]azetidine (344 mg, 1.01 mmol) (obtained as described in Reference Example 50) in dimethylformamide (1 0 ml) was added hydrazine acetate (112 mg, 1.22 mmol) at room temperature under an atmosphere of nitrogen and the mixture was stirred for 1 hour. After checking the completion of the reaction, a solution of p-nitrobenzyl (1R,5S,6S)-2-(diphenylphosphoryloxy)-6-[(R)-1-hydroxyethyl]-1-methylcarbapen-2-em-3-carboxylate (725 mg, 1.22 mmol) in acetonitrile (20 ml) was added dropwise into the resulting mixture in an ice bath under an atmosphere of nitrogen, followed by the addition of diisopropylethylamine (0.70 ml, 4.04 mmol). The mixture was stirred overnight while gradually raising the temperature to room temperature. After checking the completion of the reaction, ethyl acetate and saturated aqueous sodium hydrogencarbonate solution were added to the reaction mixture. The resulting mixture was shaken in a separatory funnel and the ethyl acetate layer was separated, washed with 0.5 M hydrochloric acid, saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column (eluant: ethyl acetate→ethyl acetate:methanol (10:1) to afford p-nitrobenzyl (1R,5S,6S)-2-{1-[4-(N-cyanomethyl-N-isopropyl-carbamoyl)-1,3-thiazol-2-yl]azetidin-3-yl}thio-6-[(R)-1-hydroxyethyl]-1-methylcarbapen-2-em-3-carboxylate (245 mg, yield 39%) as a pale yellow solid.
