Method for preparing 6, 11-bis-O-methyl-erythromycin A

The invention relates to a method for preparing 6, 11-bis-O-methyl-erythromycin A and belongs to the technical field of organic synthesis. The method comprises the following steps that clarithromycin is dissolved in an organic solvent, hexamethyl disilylamine and pyridine hydrochloride are added, stirring is conducted for a reaction, and then water is added to terminate the reaction; an organic layer is washed with water, and the solvent is removed to obtain a silanized product; the silanized product is dissolved in an organic solvent, iodomethane and potassium hydroxide are added, stirring is conducted for a reaction, and then water is added to terminate the reaction; a solvent is used for extraction of the mixed liquid, organic phases are combined, washing is conducted, and the solvent is removed to obtain a methylated product; the methylated product is dissolved in a solvent, the pH is regulated to be about 3.5 with acid, stirring is conducted for a reaction, a solvent is used for extraction after the reaction, extracted organic phases are combined, washing is conducted, and the solvent is removed to obtain crude 6, 11-bis-O-methyl-erythromycin A; crude 6, 11-bis-O-methyl-erythromycin A is recrystallized in 95% ethyl alcohol, and the product with the purity of 92.5% or above can be obtained. According to the method, reaction reagents are low in toxicity and environmentally friendly, raw materials are easy to obtain and low in cost, the reaction process is simple and convenient, the yield is high, and product separation and purification are simple.