General procedure for the synthesis of 2,4-dihydroxy-5-isopropylbenzoic acid from methyl 2,4-dihydroxy-5-isopropylbenzoate: the reaction was carried out by stirring the methyl 2,4-dihydroxy-5-isopropylbenzoate (0.24 g, 0.97 mmol) with lithium hydroxide (1 g) in a solvent mixture of methanol (10 mL) and water (10 mL) for 12 h at 50 °C, the reaction was was carried out under argon protection and equipped with a reflux condenser. Upon completion of the reaction, the reaction mixture was neutralized to pH 6 with 6N hydrochloric acid and subsequently extracted three times with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate, concentrated under reduced pressure and finally purified by medium pressure liquid chromatography (MPLC) to afford 2,4-dihydroxy-5-isopropylbenzoic acid in 100% yield. The thin layer chromatography (TLC) Rf value was 0.23 (ethyl acetate:hexane = 3:7).1H NMR (400 MHz, CD3OD) δ 7.68 (s, 1H), 6.35 (s, 1H), 3.25-3.22 (m, 1H), 1.27 (d, J = 4.0 Hz, 6H).13C NMR (100 MHz, CD3OD) δ 173.8, 163.3, 163.1, 129.2, 128.7, 105.4, 103.1, 27.7, 23.2.
