[(R)-2-hydroxy-1-(4-methoxy-benzylsulfanylmethyl)-ethyl]-carbamic acid t-butyl ester (71.3 g, 227.9 mmol) prepared in Step C was dissolved in dichloromethane (300 mL). Triethylamine (58 mL, 414.4 mmol) and trimethylacetic acid chloride (28 mL, 227.9 mmol) were added thereto, and the mixture was stirred for 6 h at 0° C. Water was added to quench the reaction. The reaction mixture was extracted with ethyl acetate, washed with saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate. The solvent was removed under reduced pressure, and the residue was purified by column chromatography to give the title compound (81.0 g, Yield 95%).
