[CH3:1][O:2][C:3]1[CH:27]=[CH:26][C:6]([CH2:7][N:8]2[C:12]3[N:13]=[CH:14][C:15]4[CH2:16][CH:17]([C:21]([O:23]CC)=[O:22])[CH2:18][CH2:19][C:20]=4[C:11]=3[CH:10]=[N:9]2)=[CH:5][CH:4]=1.[OH-].[Li+]>O1CCCC1.CO.O>[CH3:1][O:2][C:3]1[CH:4]=[CH:5][C:6]([CH2:7][N:8]2[C:12]3[N:13]=[CH:14][C:15]4[CH2:16][CH:17]([C:21]([OH:23])=[O:22])[CH2:18][CH2:19][C:20]=4[C:11]=3[CH:10]=[N:9]2)=[CH:26][CH:27]=1To a solution of ethyl 3-(4-methoxybenzyl)-6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinoline-7-carboxylate (159 mg, 0.44 mmol) in tetrahydrofuran (5 mL), methanol (2 mL) and water (3 mL) was added excess lithium hydroxide (0.5 g). The mixture was stirred at room temperature for 1.5 hours diluted with water (50 mL) and extracted with ethyl acetate (3×50 mL). The organic layer was dried with anhydrous magnesium sulfate and evaporated to dryness to give 3-(4-methoxybenzyl)-6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinoline-7-carboxylic acid as an off white solid (157 mg). 1H NMR (DMSO-d6) 400 MHz δ 12.33 (brs, 1H), 8.02 (s, 1H), 7.95 (s, 1H), 7.16 (d, J=8.0 Hz, 2H), 6.84 (d, J=8.0 Hz, 2H), 5.52 (s, 2H), 3.69 (s, 3H), 3.14-2.97 (m, 4H), 2.82-2.74 (m, 1H), 2.22-2.14 (m, 1H), 1.97-1.87 (m, 1H); LCMS [M+H]: 338.
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