Potassium carbonate (290 mg) and diethylamine (219 mL) were sequentially added to a solution of 3-({2-chloro-4-[(E)-2-cyclopentyl-1-(5-ethyl-6-methoxypyridin-2-yl)ethenyl]phenyl}sulfanyl)propyl 4-methylbenzenesulfonate (120 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 ethyl acetate. 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 3-({2-chloro-4-[(E)-2-cyclopentyl-1-(5-ethyl-6-methoxypyridin-2-yl)ethenyl]phenyl}sulfanyl)-N,N-diethylpropan-1-amine (110 mg, 80%) as a colorless oil.
