To a mixture of (1,5-dimethyl-1H-indol-7-yl)-oxo-acetic acid methyl ester (0.51 g, 2.21 mmol) and 2-(6-fluoro-1H-indol-3-yl)-acetamide (0.38 g, 2 mmol) in DMF (20 mL) was added a solution of potassium tert-butoxide in THF (1.0 M, 8.0 mL, 8.0 mmol) at room temperature. The reaction mixture was stirred at room temperature for 11 h, treated with concentrated hydrochloric acid (2 mL) and then heated at 50° C. for 2 h. The mixture was cooled to room temperature, 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 2-(1,5-dimethyl-1H-indol-7-yl)-N-[2-(6-fluoro-1H-indol-3-yl)-acetyl]-2-oxo-acetamide (170 mg, 23%) and 3-(1,5-dimethyl-1H-indol-7-yl)-4-(6-fluoro-1H-indol-3-yl)-pyyrole-2,5-dione (340 mg, 45.5%). 1H NMR (d6-DMSO, 400 MHz) δ 2.26 (s, 3H), 3.58 (s, 3H), 6.36 (d, J=3.13 Hz, 1H), 6.40˜6.45 (m, 2H), 6.73 (s, 1H), 7.11 (dd, J1=2.34 Hz, J2=9.38 Hz, 1H), 7.16 (d, J=3.13 Hz, 1H), 7.7.39 (s, 1H), 7.80 (d, J=3.13 Hz, 1H), 11.14 (s, 1H), 11.82 (s, 1H); MS (ES, m/z): C22H16FN3O2: 374.2 (M++1); 372.2 (M+−1).
