50 ml of sodium hexamethyldisilazide (1M solution in THF) and 5.3 ml of methyl iodide were added to a solution of 7.8 g of allyl 1-(4-allyloxy-3-methoxycinnamoyl)-piperidine-4-carboxylate (Example 66) in 200 ml of THF. The solution was reacted for 18 hours at room temperature. After reaction, 200 ml of an aqueous ammonium chloride solution was added to the reaction solution. The solution was extracted three times with 100 ml of ethyl acetate. The organic layer obtained was washed twice with an aqueous sodium chloride solution and dried over magnesium sulfate. Thereafter, the solvent was removed in vacuo. The oily substance obtained was subjected to column chromatography using 100 g of silica gel. From the fraction eluted with hexane and ethyl acetate=3:2, the solvent was removed in vacuo, yielding 1.1 g of allyl 1-(4-allyloxy-3-methoxycinnamoyl)-4-methylpiperidine-4-carboxylate (a compound of the present invention) as a pale yellow oil, which had the following physiochemical properties:
