1-(tert-Butoxycarbonyl)-4-phenylpiperidine-4-carboxylic acid (Bionet Co., 1.0 g), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (733 mg), 1-hydroxybenzotriazole (370 mg), morpholine (1 g) and triethylamine (0.76 ml) were dissolved in dimethylformamide (6 ml), and the mixture was stirred at room temperature for 10 hr. After completion of the reaction, 1N sodium hydroxide was added thereto. The precipitated solid was collected by filtration to give 4-(morpholin-4-ylcarbonyl)-4-phenyl-1-piperidinecarboxylic acid tert-butyl ester (907 mg, yield ds89%).
