To a suspension of imidazole (97 mg, 1.43 mmol), potassium carbonate (246 mg, 1.78 mmol) and sodium iodide (35 mg) in DMF (20 ml) was added N-[1-(butyl-4-{3-(3-chloropropoxy)phenyl}-1,2-dihydro-2-oxo-1,8-naphthyridin-3-yl]-N'-(2,6-diisopropylphenyl)urea (700 mg, 1.19 mmol), and the mixture was stirred at 50°-60° C. for 10 hours. After allowed to stand for cooling, the mixture was poured into water, extracted with ethyl acetate, and the extract was washed with water, washed with a saturated aqueous sodium chloride solution, and dried over magnesium sulfate. The residue was concentrated under reduced pressure, and purified by silica gel column chromatography (5% methanol in chloroform) to give the title compound (286 mg, 0.46 mmol).
