Sodium borohydride (52 mg) was added to a suspension of 2-[(2E)-3-(4-tert-butylphenyl)-3-(5-chloro-6-oxo-1,6-dihydropyridin-2-yl)prop-2-en-1-yl]-1H-isoindole-1,3(2H)-dione (50 mg) in methanol (2 mL) under ice-cooling, and the mixture was stirred at room temperature for one hour. Water was added to the reaction solution, followed by extraction with chloroform. The organic layer was dried over sodium sulfate and filtered. The solvent was then evaporated under reduced pressure. A solution of the resulting residue in trifluoroacetic acid (2 mL) was stirred under ice-cooling, during which sodium borohydride (50 mg) was added thereto. The mixture was stirred at room temperature for one hour. The reaction solution was ice-cooled, adjusted to a pH of 12 or more with a 1 M sodium hydroxide solution and then extracted with chloroform. The organic layer was dried over sodium 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) and then powdered with ethyl acetate. The precipitated crystals were collected by filtration and dried to give the title compound as a colorless powder (11 mg, 23%).
