[CH3:1][O:2][C:3](=[O:17])[C:4]1[CH:13]=[C:12]([O:14][CH2:15][CH3:16])[CH:11]=[C:6]([C:7]([O:9]C)=[O:8])[CH:5]=1.[OH-].[Na+]>CO>[CH3:1][O:2][C:3](=[O:17])[C:4]1[CH:13]=[C:12]([O:14][CH2:15][CH3:16])[CH:11]=[C:6]([C:7]([OH:9])=[O:8])[CH:5]=1To a solution of 5-ethoxy-isophthalic acid dimethyl ester (D43) (22 g, 92.4 mmol, 1 equiv) in MeOH (440 ml) was added 1N aqueous NaOH solution (87.8 ml, 87.8 mmol, 0.95 equiv) and the resulting solution was stirred at room temperature for 17 h. Most of the MeOH was removed in vacuo and the residue was partitioned between AcOEt and 1N aqueous NaOH solution. The aqueous layer was extracted with AcOEt, acidified to pH 1 and re-extracted with AcOEt. The second organic extract was dried over MgSO4 and concentrated in vacuo to give 5-ethoxy-isophthalic acid monomethyl ester (D45) (17 g, 82%) as a white solid. [M+H+ NH3]+=242.0, RT=2.79 min
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