A mixture of 3-(5-formyl-2,4-dimethyl-1H-pyrrol-3-yl)propionic acid (10 g, 51 mmol), 2-indolone (6.5 g, 49 mmol) and sodium hydroxide (40 g, 58 mmol) was dissolved in 50 ml of water and the reaction was stirred for 4 hr at 50 °C. After completion of the reaction, the mixture was cooled to room temperature, filtered and the filtrate was acidified with 12N hydrochloric acid to pH 3. The precipitated solid was collected by vacuum filtration, washed with 10 ml of water and dried under vacuum overnight. The crude product was washed twice with hot ethanol, then the solid was collected by vacuum filtration, washed with 10 ml of ethanol and dried under vacuum to give 13.8 g (91% yield) of (Z)-3-(2,4-dimethyl-5-((2-oxoindolin-3-ylidene)methyl)-1H-pyrrol-3-yl)propionic acid.1HNMR (360 MHz, DMSO-d6) data were as follows: δ 13.38 (s, br, 1H, NH-1'), 12.05 (s, br, 1H, COOH), 10.70 (s, br, 1H, NH-1), 7.69 (d, J=7.39 Hz, 1H, H-4), 7.53 (s, 1H, H-vinyl), 7.06 (t, J=7.39 Hz, 1H, H-6), and 6.95 (t, J=7.39Hz, 1H, H-5), 6.85 (d, J=7.39Hz, 1H, H-7), 2.63 (t, J=7.45Hz, 2H, CH2CH2COOH), 2.34 (t, J=7.45Hz, 2H, CH2CH2COOH), 2.28 (s, 3H, CH3), 2.24 ( s, 3H, CH3). Mass spectral data: MS m/z 311 ([M+1]+, 100).
