Cyclodextrins enantiodifferentiation

Figure 5. Enantiodifferentiation of camphor by host-guest complexation with a-cyclodextrin. Left The temperature dependence in light water Right comparison of the differences in the enantiodifferentiation in light versus heavy water.

Cyclodextrin Radical Recombination Direct excitation Enantiodifferentiation 101... 

Figure 3b. Enantiodifferentiation of methionol-S-oxide (6) on a chiral GC column coated with diacetyl tert. butyl silyl-P-cyclodextrin.

C. Yang, C. Ke, F. Kahee, D.-Q. Yuan, T. Mori, Y. Inoue, pH Controlled supramo-lecular enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate with capped a-cyclodextrins, Awi f. J. Chem., 2008,41, 565-568 C. Yang, T. Mori, Y. Inoue, Supramolecular enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate mediated by capped ct-cyclodextrins critical control of enantioselectivity by cap rigidity, J. Org. Chem., 2008, 73, 5786-5794. 

There are three classes of cyclic chiral selectors in use as CSPs, cyclodextrins, crown ethers and macrocyclic glycopepetide antibiotics. They can undergo host-guest complexes with small molecules if these can fit into the ring structure for enantiodifferentiation this fit needs to be stereochemicaUy controlled. 

Yao J, Yan Z, Ji J, Wu W, Yang C, M- Nishijima G, Fukuhara T, Mori Y, Inoue. Ammonia-driven chirality inversion and enhancement in enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate mediated by diguanidino-7-cyclodextrin. J Am Chem Soc 2014 136 6916-9. 

On-line two-dimensional GC-MS using a combination of J W DB-Wax and heptakis(2,6-di-0-methyl-3-0-pentyl)-p-cyclodextrin columns has been proposed in a study of enantiodifferentiation of edulans I and II, the key flavor components of the purple passion fruit [27]. The investigation was applied to a variety of purple passion fruit extracts and distillates of different origins (Kenya, Chile and Ivory Coast). In all samples analyzed, the 25enantiomers prevailed, as shown in Figure 4. 

Figure 4 Two-dimensional GC-MS enantiodifferentiation of edulans la to d in an extract of purple passion fruit from Chile (a) preseparation on achiral column (J W DB-Wax), cut 1, 16.8 to 17.1 minutes, cut 2, 19.0 to 19.3 minutes (b) separation on a chiral column [heptakis(2,6-di-0-methyl-3-0-pentyl)-P-cyclodextrin]. (From Ref. 27.)...

Carboxymethylated a-, P-, and -y-cyclodextrins seemed to be more effective water-soluble chiral NMR solvating agents for cationic aromatic amines and aromatic hydroxy amines than the corresponding native cyclodextrins. In cases of insufficient enantiomeric discrimination, an addition of paramagnetic Pr(III) and Yb(III) often leads to substantial enhancements in enantiodifferentiation. 

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