Potassium carbonate (290 mg) and diethylamine (219 μL) were sequentially added to a solution of 3-({2-chloro-4-[(E)-2-cyclopentyl-1-(5-methyl-6-oxo-1,6-dihydropyridin-2-yl)ethenyl]phenyl}sulfanyl)propyl 4-methylbenzenesulfonate (33 mg) in acetonitrile (3 mL), and the mixture was stirred at 90° C. for two hours. The reaction solution was poured into water, 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 (18 mg, 66%) as a colorless amorphous.
