1.20 g (2.76 mmol) of 2-[4-(N-acetyl-N-ethoxycarbonylmethylamino)-3-fluorophenyl]-5-amino-6,8-difluoro-4H-1-benzopyran-4-one obtained in Example 44 was dissolved in 20 ml of dimethylformamide under argon atmosphere, 111 mg of sodium hydride (60% oil dispersion) and 0.82 ml of 1-iodohexane were added under ice-cooling and the mixture was stirred at room temperature for 1.7 hours. 33 mg of sodium hydride was added and the mixture was stirred for additional 40 minutes. A 10% aqueous solution of citric acid was added to the reaction solution and the mixture was extracted 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 (chloroform:acetonitrile=10:1) to give 433 mg (28%) of 2-[4-(N-acetyl-N-ethoxycarbonylmethylamino)-3-fluorophenyl]-6,8-difluoro-5-hexylamino-4H-1-benzopyran-4-one.
