1-Acetyl-N-(3,4-dichlorophenyl)-N-{3-[4-(4-nitrobenzyl)-1-piperidinyl]propyl}-4-piperidinecarboxamide (Example 302) (70 mg, 0.12 mmol) was dissolved in ethanol (0.4 mL). To the mixture was added stannic chloride 2 hydrate (135 mg, 0.61 mmol), and the mixture was heated for 30 minutes under reflux. The mixture was cooled, and to the mixture were added aqueous solution of 1N-sodium hydroxide (10 mL) and ethyl acetate (10 mL). The resulting white precipitates were filtered off with Celite. The filtrate was subjected to extraction procedure. The organic layer was washed with saturated aqueous solution of sodium chloride, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The concentrate was subjected to column chromatography (alumina 10 g, ethyl acetate), and the desired fraction was concentrated under reduced pressure to give the titled compound (63 mg, 0.11 mmol, Yield 92%) as pale yellow oily substance.
