To a solution of (2S,4S)-1-p-nitrobenzyloxycarbonyl-4-tritylthiopyrrolidine-2-methanol (5.0 g: 9.01 mmole) in dichloromethane (50 ml) stirring at -15° C., triethylamine (1.63 ml: 1.3 eq.) and methanesulfonyl chloride (0.85 ml: 1.1 eq.) are added. The mixture is stirred at -15° to -10° C. for 30 minutes. The reaction mixture is poured into water and extracted with dichloromethane. The extract is successively washed with dilute hydrochloric acid, aqueous sodium hydrogen carbonate, and water, dried over magnesium sulfate, and concentrated in vacuo. The residue is purified by silica gel column chromatography (toluene: ethyl acetate=9:1) to give (2S,4S)-1-p-nitrobenzyloxycarbonyl-4-tritylthiopyrrolidine-2-methanol methanesulfonate (4.86 g). Yield: 85.2%. NMR δ(CDCl3) ppm: 1.65 to 1.93(m, 1H), 2.00 to 2.26(m, 1H), 2.68 to 2.92(m, 3H), 2.96(s, 3H), 3.78 to 3.98(m, 1H), 4.16 to 4.30(m, 1H), 4.38 to 4.52(m, 1H), 5.11(br s, 2H), 7.08 to 7.52(m, 17H), 8.24(d, J=9 Hz, 2H). IR ν (CHCl3) cm-1 : 1699, 1606.
