0.72 g (6 mmoles; 0.1 equivalent) of 4-dimethylaminopyridine, 12.0 g (60 mmoles; 1 equivalent) of methyl(R)-2-hydroxy-2(2-chlorophenyl)acetate and 7.8 g (78 mmoles; 1.3 equivalent) of triethylamine and 20 ml of dichloromethane were added to a dry reaction flask. The colorless solution obtained was cooled to 0° C. and then, operating at this temperature, 13.14 g (60 mmoles; 1 equivalent) of 4-nitrobenzenesulfonyl chloride as a solution in 30 ml of dichloromethane was added. The reaction mixture was stirred for 3 hours at 0° C. and 240 ml of 1N hydrochloric acid and 240 ml of dichloromethane was added drop wise, while stirring this mixture. After decanting, the dichloromethane phase is washed with dilute hydrochloric acid and then with water, before being concentrated under reduced pressure. An analytically pure sample is obtained after purifying on a silica column. In this manner, methyl(R)-2-(4-nitrophenylsulfonyloxy)-2(2-chlorophenyl)acetate is obtained: Yield: 98%. Optical purity: 99%.
