3-Chloroperbenzoic acid (31 mg) was added to a solution of 6-{(cyclopentyloxy)[4-(cyclopropylsulfanyl)phenyl]methyl}-3-(trifluoromethyl)pyridin-2(1H)-one (25 mg) in chloroform (1 mL), and the mixture was stirred at room temperature overnight. A sodium thiosulfate solution and aqueous sodium bicarbonate were added to the reaction solution, followed by extraction with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, after which the solvent was evaporated under reduced pressure. The residue was purified by preparative HPLC (Waters Sunfire 19×150 mm 5 μm, rate: 20 mL/min, eluent: A=acetonitrile, B=0.1% trifluoroacetic acid solution, gradient: 10 to 90%) to give the title compound as a colorless amorphous (7 mg, 26%).
