To a solution of thiomorpholine 1-oxide hydrochloride (340 mg) and triethylamine (0.31 mL) in N,N-dimethylformamide (25 mL) were added [2-(7-ethyl-5-{[6-(methylsulfonyl)pyridin-3-yl]oxy}-1H-indol-2-yl)-4,5-dihydro-1,3-thiazol-5-yl]acetic acid (500 mg), 1-hydroxybenzotriazole (300 mg) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (420 mg) under ice-cooling, and the mixture was stirred under ice-cooling and then at room temperature for 15 hr. Water was added to the reaction solution, and the mixture was extracted with ethyl acetate. The organic layer was washed with aqueous sodium hydrogen carbonate solution and saturated brine, dried over magnesium sulfate, filtered and concentrated under reduced pressure. The obtained residue was subjected to silica gel column chromatography (ethyl acetate:methanol=100:0 to 80:20, volume ratio), and the obtained pale-yellow crystals were recrystallized from tetrahydrofuran-ethyl acetate to give the title compound (354 mg, yield 58%) as colorless crystals. melting point 194-196° C.
