Chiral packings

A Messina, AM Girelli, M Flieger, M Sinibaldi, P Sedmera, L Cvak. Direct resolution of optically active isomers on chiral packings containing ergoline skeletons. 5. Enantioseparation of amino acid derivatives. Anal Chem 68 1191-1196, 1996. 

Fig. 7 Chiral packing of rod- and disk-shaped molecules in 2D crystal lattice...

Molecules of 43c adopt chiral packing (space group P2 ) and a helical molecular conformation, and crystallize in (E,Z) conformation which is unfavorable for the oxetane formation. The solid-state irradiation of 43c was found to give the oxetane 44c and a 3-lactam derivative 45c. The (3-lactam 45c was revealed to be enantiomerically enriched to 88% ee, whereas the other photoproduct 44c was racemic. The occurrence and the mechanism of transformation of 43c to 45c involve hydrogen abstraction by the alkenyl carbon atom. 

Nicoud, R.-M., Jaubert, J.-N., Rupprecht, I., and Kinkel, J. (1996) Enantiomeric enrichment of non-racemic mixtures of binaphthol with non-chiral packings. Chirality 8, 234-243. 

Okamoto, Y., Kawashima, M., Yamamoto, K., and Hatada, K. (1984) Useful chiral packing materials for high-performance liquid chromatographic resolution. Cellulose triacetate and tribenzoate coated on macroporous silica gel, Chem. Lett., 739-742. 

A. Satrijo, T. M. Swager, Facile Control of Chiral Packing in Poly(p-phenylene-vinylene) Spin-cast Films, Macromolecules, 2005, 38, 4054-4057. 

The simultaneous presence of a chiral selector and a charged non-chiral IPR was studied successfully [129]. The presence of a non-chiral IPR dramatically improved the separation of oppositely charged compounds on a chiral column, probably because the IPR increased retention and hence interactions with the chiral packing, as in the speciation of selenium-containing amino acids, on a crown ether column... 

Monomers decorated with chiral side-chains can induce a transfer of chirality at the supramolecular level. Indeed, several examples show that disklike molecules, designed to pile up into long reversible columns, form in fact helical columns, driven by the favorable packing of the chiral lateral substituents [30,32,93,94,99]. This chiral packing effect is strong enough to induce a chiral amplification a low amount of chiral monomer mixed with a non-chiral monomer can still drive the formation of helical columns. 

Y. Okamoto, M. Kawashima, and K. Hatada, Chromatographic resolution. 7. Useful chiral packing materials for high-performance hquid chromatographic resolution of enantiomers Phenylcarbamates of polysaccharides coated on sihca gel, J. Am. Chem. Soc. 106 (1984), 5357-5359. 

It is now well established that proteins can induce phase transitions in lipid membranes, resulting in new structures not found in pure lipid-water systems (c/. section 5.1). However, this property is not peculiar to proteins the same effect can be induced by virtually any amphiphilic molecule. Depending on the structure and nature of proteins, their interactions with lipid bilayers can be manifested in very different ways. We may further assume that the role of proteins in the biogenesis of cubic membranes is analogous to that in condensed systems, and lipids are necessary for the formation of a cubic membrane. This assumption is supported by studies of membrane oxidation, which induce a structure-less proteinaceous mass [113]. However, the existence of a lipid bilayer by itself does not guarantee the formation of a cubic membrane, as proteins may also play an essential role in setting the membrane curvature. In this context, note that the presence of chiral components e.g. proteins) may induce saddle-shaped structures characteristic of cubic membranes. (This feature of chiral packings has been discussed briefly in section 4.14)... 

In order to avoid a long and probably hopeless scanning of monomers in family (1) in a search for those which spontaneously crystallize in chiral packings, we chose the following line of work. We decided first to attach a chiral handle to the monomer (R or R ), guaranteeing such crystallization in a chiral space group. The structure of this optically active monomer then later served as a model for the construction of isomorphous chiral phases, composed, however, of optically inactive molecules. This was made possible by consideration of the relationship between the chiral handle and its environment in the model structure, coupled with the application of empirical rules of isomorphism. 

Chiral Packings. Chiral packings are used to separate enantiomers, which are mirror-image forms of the same compound. In the clinical laboratory this type of packing is used to separate and quantify drug enantiomers. 

The enantiomeric ratio was determined by HPLC analysis using a chiral column (Daicel Chiral-pack AD-H) with hexane-2-propanol as the solvent. 

La Torre, F., Sinibaldi, M. High-performance liquid chromatography on chiral packed microbore columns with the 3,5-dinitrobenzoyl derivative of trans-1,2-diaminocyclohexane as selector,... 

The classical method for separating enantiomers is to form diastereomeric compounds using a stoichiometric amount of a resolving agent. This method was described in Section 2.1.8. In this section, we discuss methods of resolution based on physical separations, including chromatography with chiral packing materials and capillary electrophoresis. 

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