Patent ID: 6670484
Filing Date: 2003-12-30
Classification: C07C,C07D

Abstract:
Process for the synthesis of R(+)&agr;-lipoic acid comprising the following stages:a) salifying of racemic thioctic acid with R(+)&agr;-methylbenzylamine (FEA), wherein the molar ratio FEA/racemic thioctic acid is between 0.45 and 0.70; b) separation by filtration of the crystallized diastereoisomeric salt of R(+)&agr;-lipoic acid-R(+)&agr;-methylbenzylamine; c) purification by re-crystallization of the diastereoisomeric salt of R(+)&agr;-lipoic acid-R(+)&agr;-methylbenzylamine, wherein the re-crystallization solvent consists of a mixture of non-polar/polar solvents, the polar solvent being maximum 20% by volume of the mixture, and the temperature of dissolution of the salt is between 50 and 75Â° C.; d) separation of the diastereoisomeric salt to obtain R(+)&agr;-lipoic acid by reaction of said salt with acids selected from the group consisting of aliphatic hydroxy carboxylic acids having 3 to 6 carbon atoms and aqueous phosphoric acid with a dilution between 2 and 10% by weight.