479 mg of 1-[(2-methoxy-3-pyridyl)methyl]-4-[2-(methylsulfonyl)phenethyl]piperidine obtained in Example 1 and 2 ml of thionyl chloride were dissolved in 50 ml of ethanol, and the mixture was heated under reflux for 2 hours. The reaction mixture was basified by adding a 1N aqueous sodium hydroxide thereto, and the mixture was extracted with dichloromethane. The organic layer was washed with brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated, and the resulting crude product was purified by silica gel column chromatography (ethyl acetate), to give 368 mg of the title compound as white crystals.
