To a mixture of (1-methyl-5-methoxy-1H-indol-7-yl)-oxo-acetic acid methyl ester (0.27 g, 1.1 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 mL, 4 mmol) at room temperature. The reaction mixture was heated at 50° C. for 7 h, cooled to room temperature, quenched with water, and the mixture extracted with ethyl acetate. The extract was washed with water, saturated aqueous sodium bicarbonate and brine, dried (sodium sulfate), filtered and concentrated. Flash column chromatography on silica gel eluting with chloroform and acetone gave 3(1-methyl-5-methoxy-1H-indol-7-yl)-4-(1H-indol-3-yl]-pyrrole-2,5-dione (210 mg, 56.5%). 1H NMR (d6-DMSO, 400 MHz) 3.52 (s, 3H), 3.56 (s, 3H), 6.35˜6.46 (m, 1H), 6.28 (d, J=2.93 Hz, 1H), 6.41 (t, J=2.44 Hz, 1H), 6.88 (t, J=6.84 Hz, 1H), 7.02 (d, J=2.44 Hz, 1H), 7.10 (d, J=3.42 Hz, 1H), 7.24 (d, J=7.82, 1H), 7.80 (d, J=2.93, 1H), 11.03 (s, 1H), 11.76 (m, 1H); MS (ES, m/z): C22H17N3O3: 372.2 (M++1); 370.3 (M+−1).
