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1 2004

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Zastosowanie ekstrakcji i technik membranowych do rozdziału stereoizomerów aminokwasów i ich pochodnych

Dżygiel P., Wieczorek P. P.

Wiadomości Chemiczne

2004

[Z] 58, 11-12

941--962

Derivatives of amino acids are known from their great biological relevance, for example can be used as pharmaceuticals, crop protection substances or food additives. In significant number of cases such substances show their biological potency only as single enantiomer. Therefore, one of the most important conditions during their production is to ensure their high optical purity. Generally, two routes to accomplish this goal are considered to be most effective. The first one is to synthesize enantiomers with the support of chiral catalyst introduced into the reaction mixture. The second approach involves the preparation of racemic mixture and in final step to separate it into single enantiomers. Considering the separation the most popular methods are enantiomers crystallization in the form of diastereoisomeric salts and chromatographic separation of racemates with application of chiral stationary phases. However, despite of their very extensive use, those methods possess several drawbacks and limitations. Among them, the most inconvenient are large use of solvents and expensive, chiral substances acting as agents responsible for the enantioseparation. Additionally, in case of chromatography some problems with non-linearity of the chromatographic process can take place. Therefore, the study on alternative ways of achieving the efficient separation of enantiomers is carried out in many laboratories. In this review, the very promising methods of the stereoisomers separation namely extraction and membrane techniques are presented and discussed. In case of extraction the examples of classical liquid - liquid extraction as well as aqueous - aqueous extraction and solid phase extraction application for amino acids enantiomers and their derivatives separation are described. The special attention is paid on the use of membrane techniques. The brief overview of applications of different membrane processes for the same purpose including the use of chiral polymer membranes, molecularly imprinted membranes, achiral membranes with chiral agents (solution free or immobilized) and liquid membranes is also presented. Finally, the examples of preparative scale processes, in which extraction and membrane techniques were used, are also discussed to show their applicability for the production of amino acids and their derivatives with high amounts and optical purity.