Sodium borohydride (11 mg) was added to a suspension of 6-{(E)-1-[3-chloro-4-(methylsulfanyl)phenyl]-2-[(1S)-3-oxocyclopentyl]ethenyl}-3-cyclopropylpyridin-2(1H)-one obtained in Example 1-71 (50 mg) in ethanol-tetrahydrofuran (2.5 mL, 4:1) under ice-cooling, and the mixture was stirred at room temperature for 30 minutes. The reaction solution was poured into 0.5 M hydrochloric acid, followed by extraction with chloroform. The organic layer was washed with brine, dried over anhydrous magnesium sulfate and filtered. The solvent was then evaporated under reduced pressure. The residue was purified by silica gel column chromatography (chloroform:methanol=10:0→9:1) to give the title compound (35 mg, 60%) as a colorless amorphous.
