(±)-1-(t-Butoxycarbonyl)-2-(2-oxo-3-butenyl)pyrrolidine (206 mg (10.86 mmol), prepared as described in Reference example 1–2)) was dissolved in tetrahydrofuran (2 ml). To the solution was added 4-methylthiophenol (107 mg, 0.86 mmol), and the resulting mixture was stirred at room temperature for 2 hours. At the end of this time, the reaction mixture was concentrated by evaporation under reduced pressure, and the resulting residue was dissolved in dichloromethane (2 ml). To the resulting mixture was added 70 wt % m-chloroperbenzoic acid (468 mg, 1.894 mmol) by portions under ice cooling, and the resulting mixture was stirred at room temperature for 2 hours. To the mixture were added an aqueous solution of 10% sodium thiosulfate and a saturated aqueous solution of sodium hydrogencarbonate in that order, and the resulting mixture was stirred and extracted with dichloromethane. The organic layer was washed with water, dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure, to give the title compound (322 mg) as a colorless oil (yield 94%).
