To a dichloromethane (3 ml) solution of 3-[6-(4-chlorophenylsulfonyl)(2,5-difluorophenyl)methyl-5-fluoropyridin-3-yl]propionic acid (100 mg, 0.21 mmol) were added 1-methylpiperazine (0.026 ml, 0.23 mmol), benzotriazol-1-ol (32 mg, 0.23 mmol), 4-methylmorpholine (0.026 ml, 0.23 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (45 mg, 0.23 mmol) at room temperature. The resulting mixture was stirred at room temperature for 16 hours. After the reaction mixture was washed with a saturated aqueous solution of sodium bicarbonate, the organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure. The residue thus obtained was subjected to flash silica gel chromatography. The fraction obtained from the dichloromethane:methanol=19:1 eluate was concentrated under reduced pressure. The residue was dissolved in ethanol (3 ml), followed by the addition of 1N hydrochloric acid (0.224 ml). After stirring at room temperature for 30 minutes, the reaction mixture was concentrated under reduced pressure. The residue thus obtained was washed with ethanol and collected by filtration to give the title compound (111 mg, 0.19 mmol, 89%) as a white solid.
