A solution of N-Boc-L-prolinol (51.2 g, 254 mmol) in dichloromethane (250 mL) was cooled to 0° C., and thereto were added p-toluenesulfonylchloride (53.4 g, 280 mmol), triethylamine (30.9 g, 42.6 mL, 305 mmol), and 4-dimethylaminopyridine (5.00 g, 40.9 mmol). After stirring overnight at room temperature, to the mixture was added water, and the aqueous layer was extracted with ethyl acetate. The organic layer was washed with water and brine, and then dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified with silica gel column (hexane/ethyl acetate=70/30 to 30/70) to give the title compound (89.7 g, 250 mmol, 99%).
