852 mg (2.03mmol) of the resulting 5-amino-2-[4-[N-(tert-butoxycarbonyl)-N-methylamino]-3-fluorophenyl]-6,8-difluoro-4H-1-benzopyran-4-one was dissolved in 30 ml of dimethylformamide under argon atmosphere, 165 mg of sodium hydride (60% oil dispersion) and 0.48 ml of 5-bromo-1-pentene were added under ice-cooling and the mixture was stirred at room temperature for 2 hours. 85 mg of sodium hydride (60% oil dispersion) and 0.24 ml of 5-bromo-1-pentene were added and the mixture was stirred for additional 1 hour. An aqueous saturated solution of ammonium chloride was added to the reaction solution and the mixture was extracted twice with ethyl acetate. The organic layer was washed with an aqueous saturated solution of sodium chloride and dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=7:1) to give 239 mg (24%) of 2-[4-[N-(tert-butoxycarbonyl)-N-methylamino]-3-fluorophenyl]-6,8-difluoro-5-(4-pentenylamino)-4H-benzopyran-4-one.
