3-Bromo-9-hydroxy-6,6-dimethyl-5,6-dihydro-benzo[b]carbazol-11-one (Compound JJ2, 20 mg, 0.056 mmol), 4-bromo-butyric acid methyl ester (7.0 μl, 0.056 mmol) and cesium carbonate (36.6 mg, 0.112 mmol) were dissolved in DMA (0.09 ml), and then stirred at room temperature for 1 hr. Thereafter, 4-bromo-butyric acid methyl ester (7.0 μl, 0.056 mmol) was added thereto and the mixture was stirred at room temperature for 3 hr, followed by further stirring at 45° C. for 30 min. The reaction solution was added with water, extracted with diethyl ether and dried over anhydrous magnesium sulfate. After the concentration under reduced pressure, the resulting residues were purified by silica gel column chromatography (ethyl acetate/hexane) to obtain 4-(3-bromo-6,6-dimethyl-11-oxo-6,11-dihydro-5H-benzo[b]carbazol-9-yl oxy)-butyric acid methyl ester. This compound was dissolved in MeOH (0.50 ml), added with aqueous solution of sodium hydroxide (6 mol/1), and then stirred at room temperature for 10 min. The reaction solution was added with hydrochloric acid (3 mol/1), extracted with diethyl ether, and dried over anhydrous magnesium sulfate and concentrated under reduced pressure to obtain white solid. This white solid was washed with methylene chloride to obtain the title compound (6.1 mg, 25%).
