To a mixture of 2,5-difluoro-4-(4-pentylphenyl)benzoic acid (28.40 mmol), 2-fluoro-4-(2-fluorophenyl)phenol (28.40 mmol), and dichloromethane (100 ml), 4-dimetylaminopyridine (34.10 mmol) is added dropwise. Then, a solution of 1,3-dicyclohexylcarbodiimide (34.10 mmol) in dichloromethane (100 ml) is added dropwise. After the addition is completed, the reaction mixture is stirred for 17 hrs at room temperature. Solid formed is filtered off, and a saturated aqueous solution of sodium chloride is added dropwise to the reaction mixture. The organic layer is washed with in the order of 3N-hydrochloric acid (300 ml), water, a saturated aqueous solution of sodium hydrogen carbonate (300 ml), and dried over anhydrous magnesium sulfate. The dichloromethane solution is concentrated under reduced pressure, purified by silica-gel chromatography, and further recrystallized to give the titled compound.
