tert-Butyl cis(±)-4-{[(4-chloro-5-ethyl-1H-imidazol-2-yl)carbonyl]amino}-3-methoxypiperidine-1-carboxylate obtained by the method described in Example (1g) (80 mg, 0.21 mmol) was dissolved in methanol (1 mL). A 4 N hydrochloric acid/ethyl acetate solution (3 mL) was added, and the mixture was stirred at room temperature for one hour. Following concentration under reduced pressure, the residue was dissolved in DMF (2 mL). Diisopropylethylamine (0.16 mL, 0.92 mmol) and ethyl 2-chloro-5-methyl-1,3-thiazole-4-carboxylate obtained in Example (38a) (70 mg, 0.34 mmol) were added, and the mixture was stirred using a microwave reactor at 160° C. for three hours. Dilute hydrochloric acid was added to the reaction solution, followed by extraction with ethyl acetate. The organic layer was washed with water, saturated aqueous sodium bicarbonate solution and brine, and dried over anhydrous sodium sulfate. Following concentration under reduced pressure, the residue was purified by silica gel column chromatography (elution solvent: hexane/ethyl acetate=4/1, 1/1, ethyl acetate) to obtain 15.3 mg of the title compound as a pale yellow solid (16%).
