Laboratorio Chimico Internazionale S.p.a.

Giovanna Falabella

Antonio Nardi

Annibale Salvi

Flavio Villani

Process for the synthesis of R(+)&#x3b1;-lipoic acid comprising the following stages: a) Salifying of racemic 6,8-halo-octanoic acid with S(&#x2212;)&#x3b1;-methylbenzylamine; b) separation by filtration of the crystallized diastereoisomeric salt of R(+)6,8-di-halo-octanoic acid-S(&#x2212;)&#x3b1;-methylbenzylamine; c) purification by re-crystallization of the diastereoisomeric salt of R(+)6,8-di-halo-octanoic acid-S(&#x2212;)&#x3b1;-methylbenzylamine; (d) separation of the diastereoisomeric salt to obtain R(+)6,8-di-halo-octanoic acid by reation of said salt with strong mineral acids in an aqueous solution with a dilution between 2 and 10% by weight; e) esterification of R(+)6,8-di-halo-octanoic acid to obtain the corresponding alkyl ester; f) reaction of the alkyl ester of R(+)6,8-di-halo-octanoic acid in an organic solvent with an aqueous solution of alkali disulfide in presence of a compound for phase transfer catalysis; g) hydolysis of the ester of R(+)&#x3b1;-lipoic acid.

Synthesis of r(+)&#x3b1;-lipoic acid

Process for the synthesis of R(&plus;)&agr;-lipoic acid comprising the following stages: a) Salifying of racemic thioctic acid with R(&plus;)&agr;-methylbenzylamine; b) separation by filtration of the crystallized diastereoisomeric salt of R(&plus;)&agr;-lipoic acid-R(&plus;)&agr;-methylbenzylamine; c) purification by re-crystallization of the diastereoisomeric salt of R(&plus;) &agr;-lipoic acid-R(&plus;)&agr;-methylbenzylamine, in which the re-crystallization solvent consists of a mixture of non-polar/polar solvents; d) separation of the diastereoisomeric salt to obtain R(&plus;)&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.

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Milan, Italy

Giovanna Falabella