2.05 g (5.26mmol) of 5-amino-6,8-difluoro-2-(3-fluoro-4-pivaloylaminophenyl)-4H-1-benzopyran-4-one obtained in Example 66 was dissolved in 50 mL of dimethylformamide under argon atmosphere, 3.6 mL (26.3 mmol) of 1,5-dibromopentane and 631 mg (15.8 mmol) of sodium hydride (60% oil dispersion) were added and the mixture was stirred at room temperature for 1.2 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:ethyl acetate=60:l) to give 1.68 g of 5-(5-bromopentylamino)-6,8-difluoro-2-(3-fluoro-4-pivaloylaminophenyl)-4H-1-benzopyran-4-one (yield: 59%).
