853 mg (2.19mmol) of 5-amino-6,8-difluoro-2-(3-fluoro-4-pivaloylaminophenyl)-4H-1-1-benzopyran-4-one obtained in Example 66 was dissolved in 20 mL of dimethylformamide under argon atmosphere, 788 mg (4.38 mmol) of 1-bromo-5-methylhexane and 266 mg (6.65mmol) of sodium hydride (60% oil dispersion) were added under ice-cooling and the mixture was stirred at room temperature for 5.5 hours. The reaction solution was cooled on ice, water was added and the mixture was extracted with ethyl acetate. The organic layer was washed once with water and once with an aqueous saturated solution of sodium chloride and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure and the residue was purified by silica gel column chromatography (chloroform: n-hexane=3:1) to give 762 mg of 6,8-difluoro-2-(3-fluoro-4-pivaloylaminophenyl)-5-(5-methylhexylamino)-4H-1-benzopyran-4-one (yield: 71%).
