145 mg (0.32 mmol) of 4-(4-chlorobenzoyl)-1-(3-methoxycarbonylbenzyl)-1,3,4,5-tetrahydrobenzo[e][1,4]diazepin-2-on obtained in step 1 was dissolved in 3 ml of THF. 1.6 ml of 1 M aqueous lithium hydroxide solution was added to the obtained solution, and they were stirred overnight. After the treatment with ethyl acetate as the extracting solvent by an ordinary method, the obtained crude product was dissolved in 5 ml of THF. 0.1 ml (0.7 mmol) of triethylamine and 0.05 ml (0.5 mmol) of ethyl chloroformate were added to the obtained solution under cooling with ice, and they were stirred for 30 minutes. A piece of ice and 50 mg (1.4 mmol) of sodium borohydride were added to the obtained mixture. The temperature was elevated to room temperature, and the obtained mixture was stirred overnight. The solvent was evaporated, and the obtained crude product was dissolved in 8 ml of dichloromethane. 0.03 ml (0.22 mmol)) of triethylamine and 0.01 ml (0.13 mmol) of methanesulfonyl chloride were added to the obtained solution under cooling with ice, and they were stirred overnight. After the treatment with ethyl acetate as the extracting solvent by an ordinary method, the crude product was obtained. After the purification by the silica gel column chromatography, the title compound was obtained.
