C([O:3][C:4]([C:6]1[C:10]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)=[C:9]([CH:17]=[O:18])[NH:8][C:7]=1[CH3:19])=[O:5])C.CO.[OH-].[K+]>O>[CH:17]([C:9]1[NH:8][C:7]([CH3:19])=[C:6]([C:4]([OH:5])=[O:3])[C:10]=1[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1)=[O:18]5-Formyl-2-methyl-4-phenyl-1H-pyrrole-3-carboxylic acid ethyl ester was dissolved in water (100 mL) and methanol (45 mL) with stirring. Added KOH (2 eq. 1.9 g) and heated in 100° C. After 2.5 h, cooled to room temperature and the remaining ester was removed by extracting into ethyl acetate (200 mL), dried and concentrated. The water layer was acidified to pH=3 using 2N HCl. The white solid was removed by filtration, rinsing with water. The solid was re-concentrated from toluene, triturated with hexanes and dried to afford 2 g (52%) of an off-white solid. 1H NMR (360 MHz, DMSO-d6) δ 12.46 (br s, 1H, CO2H), 11.95 (s, 1H, NH), 9.08 (s, 1H, CHO), 7.36 (s, 5H, ArH), 2.49 (s, 3H, CH3). MS m/z (relative intensity %, ion) found 229 (100, M+); calc. 229.2.
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