[OH:1][CH:2]1[C:10]2[C:5](=[N:6][CH:7]=[CH:8][CH:9]=2)[C:4](=[O:11])N1C1C=CC=CC=1.S(=O)(=O)(O)O.[C:23](=[O:26])(O)[O-].[Na+].[CH2:28]([O:30]CC)C.[CH3:33]CCCCC>CO>[CH3:28][O:30][C:4]([C:5]1[C:10]([CH:2]([O:1][CH3:33])[O:26][CH3:23])=[CH:9][CH:8]=[CH:7][N:6]=1)=[O:11]To a solution of 5,6-dihydro-5-hydroxy-6-phenyl-7H-pyrrolo[3,4-b]pyridin-7-one (1.99 g) in 100 mL of methanol was added concentrated sulfuric acid (6 mL). The reaction mixture was warmed to 75° C. for 3 hours. TLC indicated that all starting material had been converted. The reaction mixture was neutralized with aqueous sodium bicarbonate and evaporated in vacuo to remove the methanol. The aqueous residue was extracted with ether (3×). The organic extracts were combined, dried (K2CO3) and evaporated. The product was isolated by flash chromatography on silica gel using ethyl ether/hexane (3/2) as eluant to yield 1.02 g (59.4%).
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