Under nitrogen, to a solution of N-(3-hydroxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-6-yl)-N-[(2S)-3-phenoxy-2-(triethylsilyloxy)propyl]-tert-butoxycarbonylamine (150 mg) in dichloromethane (5 ml) were added pyridine (64 ml), 4-nitrophenyl chloroformate (116 mg) and a catalytic amount of 4-dimethylaminopyridine at 5° C. After being stirred at the same temperature for 2 hours, to this one was added about 6.8M ammonia in ethanol (0.5 ml), and the mixture was stirred at room temperature for 12 hours. The resulting mixture was pured into water, and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous magnesium sulfate, and evaporated in vacuo. The residue was purified by column chromatography on silica gel (hexane:ethyl acetate=3:1) to give N-[(2S)-3-phenoxy-2-(triethyl-silyloxy)propyl]-N-[3-carbamoyloxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-6-yl]-tert-butoxycarbonylamine (129 mg).
