Enantiorecognition on solid chiral selectors using microbatch technology: an example of limitation in case of strong association in the racemate.
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.
Roussel
Christian
C
Laboratoire Stéréochimie Dynamique et Chiralité, UMR CNRS 6180, Chirotechnologies: catalyse et biocatalyse, Université Paul Cézanne-AixMarseille III, 13397 Marseille Cedex 20, France. christian.roussel@univ.u-3mrs.fr
Rafii
Esfandiar
E
Del Rio
Alberto
A
Vanthuyne
Nicolas
N
D000327:Adsorption; D003514:Cyclohexylamines / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D012459:Salicylates / Q000737:chemistry*; D013237:Stereoisomerism; D013844:Thiazoles / Q000737:chemistry*; D053778:Thiazolidines
D003514:Cyclohexylamines; D012459:Salicylates; D013844:Thiazoles; D053778:Thiazolidines; C033089:thiazoline-2-thione