1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (30 mg) was added to a mixture of ethyl 4-[3-[4-[(carboxy)(4-isobutylphenyl)methoxy]benzoyl]indol-1-yl]butyrate (70 mg), 4-isobutylaniline (20 mg) and 1-hydroxybenzotriazole (20 mg) in dichloromethane (3 ml). After stirred at 25° C. for 4 hours, the mixture was partitioned between ethyl acetate and 1N hydrochloric acid. The organic layer was separated, washed with water and brine, and dried over magnesium sulfate. After evaporation of the solvent, the residue was chromatographed on silica gel (5 g) eluting with chloroform to give ethyl 4-[3-[4-[(4-isobutylphenyl)[(4-isobutylphenyl)carbamoyl]methoxy]benzoyl]indol-1-yl]butyrate (85 mg) as an oil.
