Separation of amino acid enantiomers by micelle-enhanced ultrafiltration

Abstract

A Micelle-enhanced ultrafiltration (MEUF) separation process was investigated that can potentially be used for large-scale enantioseparations. Copper(II)-amino acid derivatives dissolved in nonionic surfactant micelles were used as chiral selectors for the separation of dilute racemic amino acids solutions. For the alpha-amino acids phenylalanine, phenylglycine, O-methyltyrosine, isoleucine, and leucine good separation was obtained using cholesteryl L-glutamate and Cu(II) ions as chiral selector with an operational enantioselectivity (alpha(op)) up to 14.5 for phenylglycine. From a wide set of substrates, including four beta-amino acids, it was concluded that the performance of this system is determined by two factors: the hydrophobicity of the racemic amino acid, which results in a partitioning of the racemic amino acid over micelle and aqueous solution, and the stability of the diastereomeric complex formed upon binding of the amino acid with the chiral selector. The chiral hydrophobic cholesteryl anchor of the chiral selector also plays an active role in the recognition process, since inversion of the chirality of the glutamate does not yield the reciprocal enantioselectivities. However, if the cholesteryl group is replaced by a nonchiral alkyl chain, reciprocal operational enantioselectivities are found with enantiomeric glutamate selectors.

Chiral resolution of phenylalanine by d-Phe imprinted membrane considering rejection property

“…D-Phe), S LP is the amount of L-enantiomer (i.e. L-Phe), and C PD and C PL are the respective concentrations of D-Phe and L-Phe in the permeate [18]. When a D = 1, it indicates that there is no enantio-selectivity, if 0 \ a D-Phe \ 1 then the membrane exhibits a selectivity for L-enantiomers.…”

Chiral Separation in Preparative Scale: A Brief Overview of Membranes as Tools for Enantiomeric Separation

“…Finally, the non-enantioselective membranes generally are associated with other chiral recognition approaches such as enzymatic kinetic resolution [108,109], solution systems with micelles [110], and systems using chiral selectors [111][112][113][114]. They work as barriers or filtration mediums to selectively separate single enantiomers from a solution containing a racemate and enantioselective binding agents.…”

Enantioselective Extraction of Racemic Ofloxacin by Di(2-Ethylhexyl)phosphoric Acid and Tartaric Acid Derivatives as Mixed Complex Chiral Selectors

“…As a potential large scale production technique, solvent extraction has attracted a lot of researchers to make great efforts 5,6 . As is well known, the type of chiral selectors [7][8][9][10][11][12][13][14] and their enantioselectivety play the most important role in the separation efficiency for enantioselective extraction. In relation to the conclusion reported by the previous work 7 , there formed a new complex chiral extractant when mixed O,O'-dibenzoyl-(2R,3R)-tartaric acid (L-(-)-DBTA) and di(2-ethylhexyl)phosphoric acid (D2EHPA), and then both the distribution ratio and enantioselectivity are greatly improved by the formation of the complex instead of L-(-)-DBTA individually.…”