(b) Synthesis of 4-benzoylamino benzoic acid (A13): methyl 4-benzoylamino benzoate (A12, 1.00 g, 3.92 mmol) was dissolved in a mixed solvent of THF/MeOH/water (4:1:1 v/v, 30 mL), followed by addition of LiOH-H2O (0.505 g, 12.0 mmol). The reaction mixture was stirred for 17 h at room temperature. Upon completion of the reaction, it was acidified with 1 M HCl aqueous solution to pH < 7 and precipitated as a white solid. The precipitate was collected by filtration and dried under vacuum to give 4-benzamide benzoic acid (0.886 g, 94% yield) as a white solid. The product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 10.54 (br s, 1H), 8.00-7.88 (m, 6H), 7.65-7.59 (m, 1H), 7.59-7.51 (m, 2H). the LCMS analysis (positive ion mode) showed an rt of 4.84 min, m/z 242.1 [M+H]+ ; (negative ion mode) m/z 240.1 [M-H]-.
