2-Oxo-3-tert-butoxycarbonylamino-5-pivaloyl-8-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepine (1.0 g) was dissolved in tetrahydrofuran (10 ml), 60% sodium hydride (0.16 g) was added thereto under argon atmosphere, and the mixture was stirred for 30 minutes at room temperature. A solution of 2-bromoacetylthiophene (0.99 g) in tetrahydrofuran (1 ml) was added to the resultant mixture, stirred for 2 hours. The reaction mixture was poured into ice-water, extracted with ethyl acetate, the organic layer was washed succesively with water and saturated brine, and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, the residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=2:1), to thereby obtain 1.01 g of the titled compound (Yield: 76%).
