The same operation as in Example (106d) was performed using tert-butyl cis(±)-4-amino-3-butoxypiperidine-1-carboxylate obtained in Example (127d) (0.84 g, 3.0 mmol), 4-chloro-5-ethyl-1H-imidazole-2-carboxylic acid (85% content, 0.41 g, 2 mmol), WSC hydrochloride (0.77 g, 4 mmol), HOBt (0.41 g, 3 mmol), DMA (15 mL) and dichloromethane (15 mL). The resulting residue was purified by silica gel column chromatography (elution solvent: ethyl acetate/hexane=1/4, 2/3, 3/2, 4/1) to obtain 1.01 g of the title compound as a colorless solid (100%).
