To a solution of N-[1-butyl-4-(3-hydroxyphenyl)-1,2-dihydro-2-oxo-1,8-naphthyridin-3-yl]-N'-(2,6-diisopropylphenyl)urea (300 mg, 0.58 mmol), 2-pyridinethanol (71 mg, 0.58 mmol) in THF (5 ml) were added triphenylphosphine (152 mg, 0.58 mmol), and diethyl azodicarboxylate (101 mg, 0.58 mmol), and the mixture was stirred at room temperature for 40 hours. The mixture was poured into water, and extracted with ethyl acetate. The extract was washed with water, washed with a saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate. The resultant was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (ethyl acetate:hexane=5:5) and thin layer chromatography to give the title compound (43 mg, 0.07 mmol).
