25379-88-8

(1) Add 520g of 10% dilute hydrochloric acid aqueous solution to the reaction vessel, add 100g of 3,4-dimethoxyphenylacetic acid and 1.53g of glacial acetic acid while stirring at room temperature; after the addition is complete, react at 80℃ for 6h; take a sample, and HPLC detect that the reaction of the raw materials is complete; lower the reaction solution to 60℃, remove water by vacuum distillation, add 200mL of isopropyl ether to the remaining oily substance, and then freeze in the refrigerator (0℃) overnight, precipitate a white solid, filter, wash the filter cake with isopropyl ether, and dry at 55℃ to obtain pure 3,4-dihydroxyphenylacetic acid, 83.5g, with a yield of 96.9%. (2) Add 100 mL of methanol to a reaction vessel, and add 83.5 g of 3,4-dihydroxyphenylacetic acid under stirring at room temperature. After it is completely dissolved, add 4.98 g of concentrated hydrochloric acid (mass fraction 36%). After the addition is complete, react at 56 °C for 1 h. Take a sample and check by HPLC to see if the reaction is complete. Cool the reaction solution to room temperature, concentrate under reduced pressure to recover methanol, add 100 mL of water to the remaining oily substance, and then extract with methyl tert-butyl ether. Collect the organic layer and dry it. Concentrate to dryness to obtain 3,4-DIHYDROXYPHENYLACETIC ACID METHYL ESTER, 89.5 g, with a yield of 98.4%.