General procedure for the synthesis of 3-(3,4,5-trimethoxyphenyl)propionic acid from (E)-3-(3,4,5-trimethoxyphenyl)propenoic acid (by microwave radiation method): in a 100 mL Erlenmeyer flask, 3,4,5-trimethoxycinnamic acid (0.72 g, 0.003 mol) and PdCl2 (55 mg, 0.31 mmol) were suspended in 10% sodium hydroxide solution (6-10 mL), followed by batchwise addition of formic acid (8-12 mL). The mixture was reacted under microwave radiation for 3-5 min until the feedstock completely disappeared. Upon completion of the reaction, the cooled mixture was poured into ice water, acidified with 5% HCl and extracted with dichloromethane (3 x 10 mL). The organic layer was washed with water and dried with anhydrous Na2SO4. The solvent was removed by evaporation and the crude product was recrystallized by a solvent mixture of ethyl acetate and hexane to give 3-(3,4,5-trimethoxyphenyl)propionic acid as a white solid in 84% yield with a melting point of 102 °C (literature value 101-102 °C).1H NMR (CDCl3) δ: 6.70 (2H, s, H-2 and H-6), 3.84 (9H, s, 3-OCH3,4- OCH3 and 5-OCH3), 2.92 (2H, t, Ar-CH2-CH2-COOH), 2.70 (2H, t, -CH2-CH2-COOH); 13C NMR δ: 178.1 (COOH), 153.1 (C-3 and C-5), 135.87 (C-4 and C-1), 105.3 (C-2 and C-6) , 60.8 (4-OCH3), 56.1 (3-OCH3 and 5-OCH3), 35.5 (Ar-CH2-), 31.0 (-CH2-COOH).
