A solution of 5-({1-[5-(6-methoxypyridin-3-yl)-2-methylfuran-3-yl]-3-methylbutyl}amino)pyridine-2-carboxylic acid (395 mg), ethyl 3-(methylamino)propanoate (157 mg), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (230 mg), hydroxybenzotriazole monohydrate (184 mg) and triethylamine (168 μL) in N,N-dimethylformamide (10 mL) was stirred at room temperature for 4 hr. Ethyl acetate was added, the mixture was washed with saturated aqueous sodium hydrogen carbonate solution and water, and the organic layer was dried over magnesium sulfate. The solvent was evaporated under reduced pressure, and the organic layer was dried over magnesium sulfate. The solvent was evaporated under reduced pressure. The residue was purified by silica gel chromatography (5% ethyl acetate/hexane to 50% ethyl acetate/hexane) to give ethyl 3-[{[5-({1-[5-(6-methoxypyridin-3-yl)-2-methylfuran-3-yl]-3-methylbutyl}amino)pyridin-2-yl]carbonyl}(methyl)amino]propanoate (155 mg). Ethyl 3-[{[5-({1-[5-(6-methoxypyridin-3-yl)-2-methylfuran-3-yl]-3-methylbutyl}amino)pyridin-2-yl]carbonyl}(methyl)amino]propanoate was dissolved in ethanol (2 mL), tetrahydrofuran (2 mL) and 1N lithium hydroxide (0.6 mL) were added, and the mixture was stirred at room temperature for 1 hr. The solvent was evaporated under reduced pressure, and water (10 mL) was added. The mixture was neutralized with 1N hydrochloric acid under ice-cooling, and stirred for 1 hr. The resulting precipitate was collected by filtration and dried to give the title compound (100 mg, 70%).
