Triethylammonium 1-pyrrolidinyldithiocarboxylate (1.0 g, 4.03 mmol) and lithium chloride (171 mg, 4.03 mmol) were added to a tetrahydrofuran solution (50 ml) of p-nitrobenzyl (1R,5S,6S)-2-diphenoxyphosphoryloxy-6[(R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate (2.0 g, 3.36 mmol) at room temperature. The mixture was stirred at that temperature overnight in a nitrogen stream, and poured in a mixed liquid of ethyl acetate and water. The organic layer was washed with saturated saline, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The resultant residue was subjected to silica gel column chromatography (Wakogel™ C-300, n-heptane-ethyl acetate 1:1→2:3) to give p-nitrobenzyl (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-2-[(1-pyrrolidinyl)thiocarbonylthio]-1-methyl-1-carbapen-2-em-3-carboxylate (1.21 g, yield: 74%).
