Enantiorecognition on solid chiral selectors using microbatch technology: an example of limitation in case of strong association in the racemate

Abstract

When they were independently tested, the enantiomers of N,N'-bis(salicylidene)-trans-1,2-cyclohexanediamine showed a large difference in adsorption on new chiral selectors using microbatch technology. Surprisingly, when these enantiomers were applied on the same supports as a racemic mixture, no discrimination was observed even though suitable adsorption existed. When a mixture enriched in one enantiomer (scalemic mixture) was applied, the resulting supernatant contained the racemic form and the enantiomer in excess was adsorbed on the support together with a part of racemate. This behavior, which militates in favor of a strong heterochiral dimer formation in the racemate, was revealed using microbatch technology but remained hidden on classical column chromatography on chiral support. Molecular dynamics calculations corroborate this hypothesis, showing a favorite binding mode of the heterochiral dimer, which is stabilized by various inter- and intramolecular interactions. Our findings may be considered as a new limitation of microbatch technology, but they may have some inference in case of chiral amplification using the N,N'-bis(salicylidene)-trans-1,2-cyclohexanediamine enantiomers as chiral ligands.

Photoluminescence of a New Material: Cyclometalated C∧C* Thiazole-2-ylidene Platinum(II) Complexes

“…Treatment of the crude N -arylhydroxy­thiazolidine with hydrochloric acid finally yields the desired N -arylthiazole-2-thione structures (see Scheme for a possible mechanism). Some N -arylthiazole structures with (sterically demanding) alkyl substituents have been reported in the literature, but only a few examples of electronic variations of the phenyl ring can be found …”

Self‐disproportionation of Enantiomers (SDE) of Chiral Nonracemic Amides via Achiral Chromatography

“…This pioneering work was followed by numerous other examples of SDE via achiral chromatography,, as well as the theoretical modelling of chromatographic behaviour of nonracemic compounds under various conditions of achiral chromatography . As predicted by Charles and Gil‐Av, SDE via achiral chromatography turned out to be a remarkably comprehensive phenomenon observed for virtually all types of chiral compounds containing central,, axial, or helical chirality.…”

Cationic β-cyclodextrin-modified hybrid magnetic microspheres as chiral selectors for selective chiral absorption of dansyl amino acids

“…Several separation methods, including chromatography, 2,3 crystallization, 4 membrane separation 5 and nanomaterials based microbatch methodology, [6][7][8][9][10] have been developed for chiral recognition. Among them, microbatch technology developed by several research groups, [11][12][13][14][15][16][17][18][19] has been applied in enantioselective recognition of racemic compounds by a chiral solid support and has been extensively employed for evaluation and screening of a variety of solid chiral selectors as available chiral stationary phases (CSPs). Using the microbatch methodology for chiral recognition can provide rapid evaluation of the enantioselectivity of solid chiral selectors in a short analysis time with minimum amount of chiral selector and solvent consumption.…”