[NH2:1][C:2]1[C:11]([OH:12])=[CH:10][CH:9]=[C:4]([C:5]([O:7]C)=[O:6])[C:3]=1[C:13]([O:15]C)=[O:14].[OH-].[Na+]>C(O)C.O>[NH2:1][C:2]1[C:11]([OH:12])=[CH:10][CH:9]=[C:4]([C:5]([OH:7])=[O:6])[C:3]=1[C:13]([OH:15])=[O:14]A solution of dimethyl 3-amino-4-hydroxyphthalate C1-4 (11.25 g, 50 mmol) and NaOH (14.0 g, 350 mmol) in ethanol (140 mL) and H2O (50 mL) was stirred at 70° C. overnight. LCMS indicated that the reaction was complete. The reaction mixture was concentrated in vacuo, neutralized to pH<3, and filtered to yield 3-amino-4-hydroxyphthalic acid C1-5 as a white solid (9.6 g, yield: 97%), which was used directly in the next step without further purification.
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