Application of thin-layer chromatography in enantiomeric chiral analysis—an overview

Abstract

Several chiral drugs are produced and administered as pure enantiomers, whereas many others, especially of synthetic origin, are used mainly in the form of racemates. The biological and pharmacological activity of chiral compounds depends on their configuration. The racemic drugs may exhibit quite different activity from the optically pure drugs. Often only one of the enantiomers is pharmacologically active and/or even can be toxic. Since numerous enantiomers have been shown to behave differently from at least one point of view, whether pharmacokinetic, pharmacodynamic, toxicological or interaction, there seems to be hardly any exception to the general rule that a racemate cannot be considered as a single drug entity. A variety of chromatographic methods have been developed for optical resolution recently. Usually direct separation of the enantiomers is carried out on HPTLC chiral precoated plates or on plates impregnated with chiral substances. TLC techniques are a developing branch of separation and quantitation of drugs, both in pharmaceutical dosage forms and in biological material. This review presents an overview of the current successful enantioseparations of drugs by TLC and their potential in the analysis of the drug racemates. Copyright © 1999 John Wiley & Sons, Ltd.

Cysteine-based chiral selectors for the ligand-exchange separation of amino acids☆

“…With this procedure, an approximated amount of 0.068 g of (R)-SBC, 0.057 g of (R)-SDC and 0.045 g of (R)-STC were hydrophobically bound to the RP-18 sorbent surface. These amounts almost linearly opposite the bulkiness of the selector side chain, thus showing a different hydrophobic coating of the reversed-phase material [27].…”

Chiral separation by chromatographic and electromigration techniques. A Review

“…However, only one type of TLC plate containing a chiral stationary phase, which is based on the LEC-principle, is commercially available. Details about applications of chiral TLC to different compound classes can be found in specialized reviews [9,311,312].…”

“…The reader will be referred to specialized review articles for details. Several recent comprehensive reviews and book articles summarize chromatographic [3][4][5][6][7][8][9] and electrophoretic methods [10][11][12][13][14][15][16][17] for chiral separation in general.…”

Chiral chromatographic separation of β-blockers

“…Chiralcel OD [2][3][4][5][6][7], cyclodextrin bonded column [8][9][10][11], and Pirkle-1J column [12]. Aboul-Enein et al have used a different approach by synthesizing molecularly imprinted polymers (MIP) of (S)-timolol and using this CSP in thin layer chromatography (TLC) method for the separation of ␤-blockers like propranolol, atenolol, timolol, nadolol with calcium channel blocker nifedipine and verapamil [13]. Bhusan et al have carried out direct enantiomeric resolution of atenolol, metoprolol and propranolol by impregnating TLC using l-lysine, l-arginine [14] and l-aspartic acid [15] as chiral selectors.…”