Patent ID: 6900296

Claim:
A process for selective methylation of a hydroxy group at the 6-position of an erythromycin A derivative which comprises methylating the erythromycin A derivative with a methylating agent in a mixture of toluene and a polar aprotic solvent in the presence of a base, wherein the erythromycin A derivative is an erythromycin A having no substituent group or having substituent groups in place of(1) hydrogen atom(s) of the 2′ and/or 4″ hydroxy groups or (2) one or both methyl groups of the 3′-dimethylamino group or (3) hydrogen atom(s) of the 2′ and/or 4″ hydroxy groups, and a methyl group of 3′-dimethylamino group, wherein the substituent group is selected from the group consisting of trimethylsilyl or carbobenzyloxy.