Patent ID: RE39560

Claim:
A process for preparing a 6-O-methylerythromycin A derivative represented by the formula: wherein R 1 is: a 2-alkenyl group having 3 to 15 carbon atoms, a benzyl group, or a benzyl group substitued substituted by 1 to 3 of a chlorine atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or an alkoxycarbonyl group having 2 to 6 carbon atoms, and R 2 and R 3 are trimethylsilyl, which comprises reacting, in any desired sequence, erythromycin A 9-oxime with a compound of formula R 1 —X (wherein R 1 is as defined above, and X is a halogen atom) and with a substituted silylating agent having an R 2 group to give a compound represented by the formula ; : (wherein R 1 , R 2 and R 3 are as defined above), and then reacting said compound of formula II with a methylating agent selected from the group consisting of methyl bromide, methyl iodide, dimethyl sulfate, methyl p-toluene sulfonate and methyl methane sulfonate, the amount of said methylating agent being 1-3 molar equivalents of said compound of formula II, said trimethylsilyl group (R 2 ) protecting the 2′ hydroxyl group against methylation and preventing the 3′-dimethylamino group from being quaternized with the methylating agent.