S-Trityl-(R)-Cysteine, a Multipurpose Chiral Selector for Ligand-Exchange Liquid Chromatography Applications

Abstract

The stratification of 0.040–0.050 g of S-trityl-(R)-cysteine ((R)-STC) onto a conventional ODS phase produces a very effective (α and RS up to 5.71 and 12.09, respectively) and stable (more than 30 days of repeated analysis) chiral ligand-exchange chromatography (CLEC) coated chiral stationary phase (C-CSP). With a few specific exceptions, a (R) < (S) enantiomer elution order can be easily predicted. The (R)-STC-based C-CSP can be successfully exploited also at a preparative level for enantioisolations of CNS active amino acids (AAs), with a racemate loadability up to 0.015 g for single injection. The CLEC (R)-STC-based system can be helpful in monitoring the presence of (R)-AAs in edible products and other organic materials, thus contributing to evaluating product quality and diagnosing subclinical pathological states in animals and humans. Very profitably, molecular modeling–based computer-assisted classification analyses can reveal the actual enantioseparation ability of the (R)-STC phase towards a specific compound.