Triethylamine → (2S)-1-(t-Butoxycarbonyl)-2-[1-hydroxy-2-(4-methoxyphenylthio)ethyl]pyrrolidine

4-Methoxythiophenol (1.0 ml) and triethylamine (1.0 ml) were added to (2S)-1-(t-butoxycarbonyl)-2-(1,2-epoxyethyl)-pyrrolidine (1.57 g) as obtained in Example 1-A) in methanol (50 ml), and the mixture was stirred for 1.5 hours under reflux. The reaction mixture was concentrated and the residue was poured into ice-water, followed by extraction with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate and concentrated. The residue was recrystallized from a mixted solution of hexane-ethyl acetate to give 2.16 g of the title compound as colorless needles.