Method of synthesizing levorotatory p-hydroxyphenylglycine compounds

A method of synthesizing a levorotatory p-hydroxyphenylglycine having the structure of formula I,

• characterized in that, the method comprises the following steps:
• step 1:
• the compound of formula II and the compound of formula III undergo nucleophilic addition reaction in a first solvent, to produce the compound of formula IV;
• wherein the first solvent is selected from the group consisting of ether solvent, ester solvent, haloalkane solvent, C5˜C10 hydrocarbon solvent, nitrile solvent, and ketone solvent;
• step 2:
• the compound of formula IV and the compound of formula V undergo a Friedel-Crafts-like reaction in a second solvent, using acid as catalyst, to produce the levorotatory p-hydroxyphenylglycine compound having the structure of formula VI;
• wherein the second solvent is selected from the group consisting of nitrile solvent, haloalkane solvent, C5-C10 hydrocarbon solvent;
• the acid is a chiral acid or an achiral acid, wherein the chiral acid is selected from the group consisting of D-tartaric acid, L-tartaric acid, D-camphorsulfonic acid, L-camphorsulfonic acid, L-proline, D-proline, and chiral phosphoric acid, and the achiral acid is selected from the group consisting of methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and hydrochloric acid;
• wherein, R1 is selected from the group consisting of acetyl, benzoyl, tert-butoxycarbonyl, benzyloxycarbonyl, formamido, and pivalyl;
• R2 is selected from the group consisting of methyl, ethyl, isopropyl, tert-butyl, and benzyl;
• and R3 is hydrogen;
• step 3:
• in a mixed solution of alcohol and water, or in water, the compound of formula VI undergoes hydrolysis reaction by adjusting the pH value to be <2, then the solution is neutralized with a base to a pH value of 5.2˜5.6, to obtain the compound of formula I.