Ethyl 3-aminobenzoate (310 mg) was dissolved in tetrahydrofuran (50 ml), triphosgene (187 mg) was added under ice-cooling, triethylamine (161 μl) was added five times every 3 minutes,a solution of 1-(2-toluoylmethyl)-2-oxo-3-amino-5-(2-pyridylcarbonyl)-8-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepine (730 mg) in tetrahydrofuran (23 ml) was added thereto, and the reaction mixture was allowed to come to room temperature, stirred for 2 hours. The reaction mixture was concentrated under reduced pressure, water (50 ml) was added, extracted with methylene chloride. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography(chloroform:ethyl acetate=10:1), to thereby obtain 483 mg of the titled compound.
