To a mixture of (1-methyl-4-methoxyl-1H-indol-7-yl)-oxo-acetic acid methyl ester (0.27 g, 1.10 mmol) and 2-(1H-indol-3-yl-acetamide (0.17 g, 1 mmol) in DMF (5 mL) was added a solution of potassium tert-butoxide in THF (1.0 M, 4.0 mL, 4.0 mmol) at room temperature. The reaction mixture was heated at 60° C. for 4 hrs, cooled to room temperature, and quenched with hydrochloric acid (1.0 N). After stirring at room temperature for 30 min, the mixture was extracted with ethyl acetate and the extract was washed with water, saturated aqueous sodium bicarbonate and brine, dried (sodium sulfate), filtered and evaporated. Flash column chromatography on silica gel eluting with chloroform and acetone gave 3-(1H-indol-3-yl)-4-(4-methoxy-1-methyl-1H-indol-7-yl)-pyrrole-2,5-dione (270 mg, 72.7%). 1H NMR (d6-DMSO, 400 MHz) 3.65 (s, 3H), 3.84 (s, 3H), 6.46˜6.55 (m, 4H), 6.78 (d, J=7.6 Hz, 1H), 6.95 (t, J=7.2 Hz, 1H), 7.13 (d, J=3.2 Hz, 1H), 7.32 (d, J=8.0 Hz, 1H), 7.86 (d, J=3.2 Hz, 1H), 11.05 (s, 1H), 11.79 (s, 1H); MS (ES, m/z): C22H17FN3O3: 372.19(M++1), 370.29 (M+−1).
