To 20 mL of a tetrahydrofuran solution containing 1.7 g of 1-tert-butyl 4-ethyl 4-(3-hydroxypropyl)piperidine-1,4-dicarboxylate, 0.82 mL of triethylamine and 0.58 mL of methane sulfonylchloride were added at 5° C., and the mixture was stirred at room temperature for 1 hour. Ethyl acetate and water were added thereto. The organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layer and the extract were combined, the resultant solution was washed with an aqueous saturated sodium chloride solution and dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to obtain 1.9 g of a colorless oily substance, 1-tert-butyl 4-ethyl 4-(3-((methanesulfonyl)oxy)propyl)piperidine-1,4-dicarboxylate.
