[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:10](=[CH:11][C:12]=1[O:13][CH3:14])[C:9](=[O:15])[NH:8][CH2:7]/[C:6]/2=[CH:16]\[C:17]([O:19]CC)=[O:18].[Li+].[OH-]>CO.C1COCC1>[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:10](=[CH:11][C:12]=1[O:13][CH3:14])[C:9](=[O:15])[NH:8][CH2:7]/[C:6]/2=[CH:16]\[C:17]([OH:19])=[O:18]To a stirred solution of (Z)-ethyl 2-(6,7-dimethoxy-1-oxo-2,3-dihydroisoquinolin-4(1H)-ylidene)acetate (1.45 g, 5 mmol) in MeOH (20 mL) and THF (40 mL) was added 2N LiOH (5 mL) dropwise at room temperature and the resulting mixture was stirred at room temperature overnight. The reaction was quenched by addition of 1N HCl and the solvents were removed under reduced pressure. The mixture was diluted with water and cooled and the precipitate collected by filtration to afford (Z)-2-(6,7-dimethoxy-1-oxo-2,3-dihydroisoquinolin-4(1H)-ylidene)acetic acid (1.0 g, 77%). LC-MS (ES-API); rt 7.21 min; m/z calculated for C13H13NO5 [M−H]− 262.0, found 262.1.
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