Methyl 6-[(aminocarbonothioyl)amino]hexanoate (335 mg, 1.64 mmol) was dissolved in methanol (10 mL), a 1 N aqueous sodium hydroxide solution (2.46 mL, 2.46 mmol) was added, and the mixture was stirred at room temperature for 4 hours. After the reaction was completed, 1 N hydrochloric acid (2.46 mL, 2.46 mmol) was added, and then the solvent was evaporated under reduced pressure. The resulting residue was dissolved in dichloromethane, 1-[2-(methylamino)ethyl]piperidin-4-yl biphenyl-2-ylcarbamate (578 mg, 1.64 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (469 mg, 2.46 mmol) and triethylamine (0.342 mL, 2.46 mmol) were added, and the mixture was stirred overnight at room temperature. After the reaction was completed, a saturated aqueous sodium hydrogencarbonate solution was added, the mixture was extracted 3 times with methylene chloride, and the resulting organic layer was dried with anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, and the resulting residue was purified by NH silica gel column chromatography (elution solvents, n-hexane:ethyl acetate:methanol=1:1:0→0:10:0→0:9:1, v/v/v) to give the title compound (291 mg; yield, 34%).
