1.00 g (2.87 mmol) of Compound 27 obtained in Example 27 was dissolved in 10 ml of dimethylformamide under argon atmosphere, 355 mg of potassium tert-butoxide and 1.02 ml of ethyl 6-bromohexanoate were added under ice-cooling and the mixture was stirred at room temperature for 4.5 hours. An aqueous ammonium chloride solution 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, dried over anhydrous sodium sulfate and purified by silica gel column chromatography (chloroform:methanol=30:1) to give 1.26 g (85%) of 2-[4-[N-acetyl-N-(5-ethoxycarbonylpentyl)amino]-3-fluorophenyl]-5-amino-6,8-difluoro-4H-1-benzopyran-4-one.
