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1. WO2006100691 - A PROCESS FOR THE PREPARATION OF 6-O-METHYL ERYTHROMYCIN A DERIVATIVE

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[ EN ]

im:

A process for the preparation of 6-O-methylerythromycin A derivative which comprises the selective methylation of erythromycin A derivative of formula π,

Formula II


wherein R is hydrogen atom or a substituent group such as a lower alkyl group, which is substituted or unsubstituted, an aryl substituted methyl group, a substituted oxyalkyl group, or a thioalkyl group; R; is 2 ',4 "-bistrimethylsilyl, 2 '— carbobenzyloxy, 3 '—dicarbobenzyloxy or other hydroxyl protecting group.

with a methylating agent in a mixture of a acyclic or cyclic alkane having C6-Cio carbon atoms, and a polar aprotic solvent in the presence of a base, under mild conditions.

The process according to claim 1, wherein the acyclic or cyclic alkane is selected from hexanes, heptanes and cyclohexane containing C6-Ci0 carbon atoms.

The process according to claim 1, wherein acyclic or cyclic alkane is cyclohexane.

The process according to claim 1, wherein the reaction is conducted at temperature between 12 to 60°C.

The process according to claim 2, wherein the reaction is conducted at temperature between 15 to 3O0C.

The process according to claim 1, wherein the methylating agent is methyl iodide, methyl bromide, methyl chloride and dimethyl sulphate.

The process according to claim 1 , wherein the polar aprotic solvent is selected from the group consisting of iV,iV-dimethylformamide, iV,iV-dimethyl acetamide, dimethyl sulphoxide, 1 ,2-dimethoxyethane and hexamethyl phosphoric triamide

The process according to claim 7, wherein the polar aprotic solvent is dimethyl sulphoxide.

The process according to claim 1, wherein the base is potassium hydroxide, sodium hydroxide, sodium hydride or potassium hydride.

The process according to claim 9, wherein the base is potassium hydroxide.

The process according to claim 1, wherein 6-O-methylerythromycin A derivative is converted to clarithromycin of formula I, Formula I

wing conventional methods.