A mixture of 2-(3-bromophenoxy)-3-[3-(3,5-dimethoxypyridin-4-yl)propoxy]pyridine (3.15 g, 7.1 mmol) obtained in Example 19 and pyridine hydrochloride (8.0 g) is stirred at 180° C. for 1.5 hours. After being allowed to cool, to the mixture is added a saturated aqueous sodium hydrogen carbonate solution (100 ml), and the mixture is extracted with ethyl acetate (100 ml×3). The organic layer is washed with a saturated brine (50 ml×2), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue is purified by silica gel column chromatography (eluent: chloroform/methanol) to give 2-(3-bromophenoxy)-3-[3-(3-hydroxy-5-methoxypyridin-4-yl)propoxy]pyridine and 2-(3-bromophenoxy)-3-[3-(3,5-dihydroxypyridin-4-yl)propoxy]pyridine, which are individually treated with fumaric acid to give 2-(3-bromophenoxy)-3-[3-(3-hydroxy-5-methoxypyridin-4-yl)propoxy]pyridine.0.5 fumarate (1.00 g) [m.p. 157-161° C. (recrystallized from ethanol/diethyl ether)] and 2-(3-bromophenoxy)-3-[3-(3,5-dihydroxypyridin-4-yl)propoxy]pyridine.0.5 fumarate (1.36 g) [m.p. 184-189° C. (recrystallized from ethanol)], respectively.
