To a solution of 1-(p-nitrobenzyloxycarbonyl)-4-hydroxypiperidine (10.54 g) in dry pyridine (105 ml) was added p-toluenesulfonyl chloride (14.35 g) at 0° C., followed by stirring at 25° C. for 23 hours. The reaction mixture was diluted with water and extracted with diethyl ether-dichloromethane (9:1). The extract was washed successively with saturated aqueous sodium chloride, 1N hydrochloric acid, saturated aqueous sodium chloride and saturated aqueous sodium bicarbonate, dried over anhydrous sodium suflate and evaporated to give 1-(p-nitrobenzyloxycarbonyl)-4-(p-toluenesulfonyloxy)piperidine.
