3-((5-fluoro-2-oxoindolin-3-ylidene)methyl)benzoic acid (283 mg, 1 mmol) and 8 ml of DMF were stirred at room temperature while 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (394 mg, 2 mmol), hydroxybenzo-triazole (162 mg, 1.2 mmol), triethylamine (404 mg, 4 mmol) and 6-aminocaproic acid methyl ester hydrochloride (219 mg, 1.2 mmol) were added. The mixture was stirred for 24 hours at room temperature. The mixture was diluted with 400 mL of brine. The solids were collected by vacuum filtration, washed with water and dried under vacuum to give the title compound (332 mg, 81% yield) as a brown solid. LC-MS (m/z) 411 (M+1).
