GENERAL METHOD: Methyl 3-hydroxy-5-methoxybenzoate (4.5 g, 16.7 mmol) was dissolved in methanol (30 mL) and 1M sodium hydroxide solution (60 mL, 60 mmol) was added under nitrogen protection. The reaction mixture was stirred at 45 °C for 1-2 h. The progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction solution was acidified with 1 M hydrochloric acid (50 mL) and subsequently extracted with ethyl acetate (3 x 50 mL). The organic phases were combined, washed with distilled water (2 × 30 mL) and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to give 3-hydroxy-5-methoxybenzoic acid (5a) as an off-white solid (4.02 g, 94% yield) with a melting point of 196-198 °C.1H NMR (400 MHz, acetone-d6) δ (ppm): 7.42-7.33 (5H, m, benzyl Ph), 7.21 (1H, dd, J = 2.4,1.2 Hz. H-2), 7.11 (1H, dd, J = 2.4,1.2Hz, H-6), 6.68 (1H, t, J = 2.4Hz, H-4), 5.07 (2H, s, benzyl CH2). The obtained 1H NMR spectrum is in agreement with data reported in the literature [38].
