C([O:3][C:4]([C:6]1[N:7]([CH3:20])[C:8]2[C:13]([CH:14]=1)=[CH:12][C:11]([C:15]([O:17]CC)=[O:16])=[CH:10][CH:9]=2)=[O:5])C.[OH-].[Na+]>O.CO>[CH3:20][N:7]1[C:8]2[C:13](=[CH:12][C:11]([C:15]([OH:17])=[O:16])=[CH:10][CH:9]=2)[CH:14]=[C:6]1[C:4]([OH:5])=[O:3]Solution of 1-methyl-indole-2,5-dicarboxylic acid diethyl ester 17 (675 mg, 2.5 mmole) and NaOH (5.00 mmole) in a mixture of water/MeOH (1/4) (20 ml) was stirred at 50° C. for 4 h and then overnight at ambient temperature. The reaction mixture was evaporated in vacuo to dryness and the residue was dissolved in water (20 ml) and acidified with 1M HCl up to pH=3. The precipitate was collected on the filter and washed with water (3×5 ml) and dried over phosphorus pentoxide in dessicator to give 488 mg (89%) of 1-methyl-indole-2,5-dicarboxylic acid 18 as white crystalline material. MS: 218.2 (M−H). 1H-NMR (DMSO-d6): δ 8.35 (m, 1H, H-4, indole); 7.90 (m, 1H, H-6, indole); 7.41 (d, 1H, H-7, indole); 7.32 (s, 1H, H-3, indole); 4.05 (s, 3H, NCH3, indole).
Loading…
