N-[3-(3,4,5,6-Tetramethoxy-2-methylbenzyl)-2-(4-pyridyl)benzoyl]piperidine (74 mg, 0.1510 mmol) was dissolved in a mixed solvent of acetonitrile (9 ml) and water (3 ml), then CAN (206 mg, 0.3759 mmol) was added thereto at room temperature and the mixture was stirred for 1 hour. The reaction solution was poured into water, neutralized with a saturated aqueous solution of sodium hydrogen carbonate and extracted with ethyl acetate. The extract was washed with water and dried and the solvent was evaporated therefrom. The residue was purified by preparative thin layer silica gel (hexane:ethyl acetate=1:5) to give the title compound (32 mg, 0.0695 mmol, 46%).
