To a solution of 3-[(3-methyl-4-oxo-1,4-dihydropyridin-2-yl)methoxy]-5-(tetrahydro-2H-pyran-4-ylmethoxy)benzonitrile (100 mg) in DMF (2 mL) were added sodium azide (18 mg) and ammonium chloride (15 mg), followed by stirring at 100° C. for 24 hours. The reaction mixture was concentrated under reduced pressure, and the residue was dissolved in a 1M aqueous sodium hydroxide solution and washed with diethyl ether. The aqueous layer was adjusted to a pH of 2 by adding 1M hydrochloric acid, followed by extraction with chloroform and a mixed solvent of chloroform-methanol (5:1). The organic layer was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by thin layer chromatography (developer: chloroform/methanol=6/1) and washed with ethyl acetate to obtain 3-methyl-2-{[3-(tetrahydro-2H-pyran-4-ylmethoxy)-5-(1H-tetrazol-5-yl)phenoxy]methyl}quinolin-4(1H)-one (37 mg).
