To an ice-cooled and stirred solution of methyl 7-hydroxy-5-{[6-(methylsulfonyl)pyridin-3-yl]oxy}-1H-indole-2-carboxylate (1.2 g) and potassium carbonate (0.50 g) in N,N-dimethylformamide (10 mL)-tetrahydrofuran (30 mL) was added ethyl iodide (0.28 mL), and the mixture was stirred at room temperature for 18 h and then at 55° C. for 15 h. The reaction mixture was concentrated in vacuo. The residue was partitioned between ethyl acetate and aqueous citric acid solution. The organic layer was washed successively with water and brine, dried (MgSO4), filtered, and concentrated in vacuo. The residue was purified by silica gel chromatography (ethyl acetate:hexane=25:75 to 40:60, volume ratio) to give the title compound (0.65 g, 50%) as light yellow crystals. MS 391 (MH+).
