1. S-trityl-(R)-cysteine, a multipurpose chiral selector for ligand-exchange liquid chromatography applications
Roccaldo Sardella, Federica Ianni, Antonella Lisanti, Stefania Scorzoni, Maura Marinozzi, Benedetto Natalini Crit Rev Anal Chem. 2015;45(4):323-33. doi: 10.1080/10408347.2014.937851.
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.
2. Spiro[2.2]pentane as a dissymmetric scaffold for conformationally constrained analogues of glutamic acid: focus on racemic 1-aminospiro[2.2]pentyl-1,4-dicarboxylic acids
Roberto Pellicciari, et al. J Org Chem. 2002 Aug 9;67(16):5497-507. doi: 10.1021/jo020138v.
In search for novel conformationally constrained analogues of L-glutamic acid, a diastereodivergent synthesis of the four 1-aminospiro[2.2]pentyl-1,4-dicarboxylic acid racemic pairs is reported along with their stereochemical assignment, conformational analysis, and preliminary biological evaluation as potential glutamate (ionotropic and metabotropic) ligands.
3. Dynamic ligand-exchange chiral stationary phase from S-benzyl-(R)-cysteine
B Natalini, R Sardella, A Macchiarulo, R Pellicciari Chirality. 2006 Aug;18(7):509-18. doi: 10.1002/chir.20280.
S-benzyl-(R)-cysteine (R-SBC) is a new chiral ligand-exchange stationary phase which has proved to be effective in the analytical separation of some natural and unnatural underivatized amino acids with fair to good separation and resolution factors. The dynamic coating of the RP-18 solid support with S-Benzyl-(R)-cysteine (R-SBC) gives rise to a stable and efficient chiral stationary phase (CSP) that has been successfully employed. The mechanism of chiral recognition is discussed and a molecular modeling study aimed at identifying molecular descriptors responsible for observed different behaviours of analytes upon different albeit closely related selectors is discussed.
