Chiral separation of unmodified α‐hydroxy acids by ligand exchange HPLC using chiral copper(II) complexes of (S)‐phenylalaninamide as additives to the eluent

Abstract

Copper(I1) complexes of 6)-phenylalaninamide have been successfully used for the direct enantiomeric separation of unmodified (R, S)-a-hydroxy acids in reversed phase high-performance liquid chromatography (RP-HPLC). The effect of various parameters (pH, eluent polarity, selector concentration) on enantioselectivity is discussed. Evidence is provided that a mechanism of ligand exchange is actually occurring during the chromatographic separation. The method is very convenient and easy to use, and the chu-a1 selector is commercially available and can be recovered at the end of the analysis. A conventional achiral RP-ODS-2 column is used and no pretreatment of the samples is required. This method allows the accurate determination of the enantiomeric excess of a-hydroxy acids in synthetic and biological samples. o 1995 WiIey-Liss. Inc.

Chiral separation by chromatographic and electromigration techniques. A Review

“…Subsequently, a large number of chiral LEC phases and their applications have been published [236][237][238]. Recent developments are the preparation of a chiral stationary phase by covalent attachment of S-and R-phenylalaninamide [239] and (S,R)-and (S, S) -N 2 -(2-hydroxypropyl)-phenylalaninamide [240] to silica. G . u ubitz et al [241] prepared two new chiral ligand-exchange chromatography (CLEC-) phases by binding l-proline via a (2-hydroxycyclohexyl)ethylene and a 6-hydroxy-4-oxa-8-aza-n-decene spacer to silica.…”

“…Numerous publications deal with the application of this basic technique using different metal complexes [236][237][238]. Selected examples of recent developments in this field are the use of (S)-phenylalaninamide [239], (S,S)-N 2 -(2-hydroxypropyl)-phenylalaninamide [240] and (S,S)-N,N'-bis(phenylalanyl)ethanediamine as chiral additives to the mobile phase.…”

Direct separation of ?-hydroxy acid enantiomers by ligand exchange chromatography

“…11 Similar techniques employing the CSP 9,10,12-14 or CMP 15,16 method were used to resolve racemic mixtures of ␣-hydroxy acids. Davankov and Rogozhin suggested a theoretical model for the key process leading to the enantiomeric separation of ␣-amino acids.…”

Study of enzyme-catalysed polymerization of lactic acid by HPLC and MALDI-MS

“…Literature references were found for chiral separation of lactic acid by HPLC method, using coated porous graphite stationary phase (Knox and Wan, 1995) and using chiral copper (II) complexes of (S)-phenylalanineamide as additives to the eluent (Galaverna et al, 1995). The optical purity of D-lactic acid was determined by gas chromatography using chiral stationary phase and by high-performance liquid chromatography (HPLC) using the Pirkle-type phase (Marcenac et al, 1996).…”