Alternatively, (R)-3-amino-3,4-dihydrocarbostyril hydrochloride (95 mg) was added to a mixture of tetrahydrofuran (10 mL), 5-chloroindole-2-carboxylic acid (103 mg), 1-hydroxy-7-azabenzotriazole (85 mg), and 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (120 mg) at room temperature. Diisopropylethylamine (186 mg) was added, and the resulting yellow suspension was stirred for 2 h, during which a solution formed. The solution was diluted with ethyl acetate (50 mL) and washed sequentially with 1.0 M aqueous hydrochloric acid (25 mL), 1.0 M aqueous sodium hydroxide (25 mL), and brine (25 mL), dried over anhydrous sodium sulfate, and evaporated under vacuum. The resulting solid crude product was triturated with diethyl ether (5 mL twice), then 50% methanol in diethyl ether (5 mL twice). Drying under vacuum provided pure title compound (132 mg).
