In 30 ml of xylene, 1.10 g of 1-tert-butoxycarbonyl-1,2,5,6-tetrahydropyridine-3-methanol (which had been prepared by the method described in Tetrahedron, Vol. 54, No. 25, p. 7045, 1998), 914 mg of ethyl orthoformate and 130 mg of 2,4-dinitrophenol were dissolved, and the formed solution was heated to 140° C. and stirred for 7 hours while removing the ethanol as formed. The reaction liquid was cooled, then ethyl acetate was added thereto and the organic layer was successively washed with 1N hydrochloric acid, saturated aqueous sodium hydrogencarbonate solution and saturated brine, dried over anhydrous sodium sulfate and removed of the solvent by distillation. The resulting residue was purified on silica gel column chromatography (hexane/ethyl acetate=10/1) to provide 692 mg of 1-tert-butoxycarbonyl-3-methylenepiperidine-4-acetic acid ethyl ester. The product was dissolved in 20 ml of tetrahydrofuran, cooled to 0° C., 111 mg of lithium aluminium hydride was added thereto, and stirred for an hour. Then an excessive amount of sodium sulfate decahydrate was added to the reaction liquid and stirred for 15 minutes. The resulting mixture was filtered, and the filtrate was concentrated to provide 558 mg of crude 1-tert-butoxycarbonyl-3-methylenepiperidine-4-ethanol.
