Chiral separation gas chromatography

Koppenhoefer, B., Nothdurft, A., Pierrot-Sanders, J., Piras, P.,Popescu, P, Roussel, C., Stiebler, M., and Trettin, U. 1993. CHIRBASE A graphical molecular database on the separation of enantiomers by liquid, supercritical fluid, and gas chromatography. Chirality 5 213-219. 

In gas chromatographic chiral separation, useful information may be obtained from the peak parameters depicted in Table 1. Enantioselectivity — Ak s(AG°) (cf. (2) in Table 1) arises from the diastereomeric interaction between the enantiomers of the selectand and the selector. Assuming a fast and reversible equilibration, enantiomer separation by gas chromatography is governed by thermodynamics according to the Gibbs-Helmholtz equation (the subscripts refer to enantiomers R and S) ... 

Figure 7 Enantiomer separation of methyl 2-chloropropanoate by gas chromatography on heptakis(3-0-trifluoroacetyl-2,6-di-0-/>pentyl)-)5-cyclodextrin (23) (undiluted) at three temperatures. Column 20 m x 0.25 mm (i.d.) nondeactivated fused-silica capillary. (From Berthod A, Li W, and Armstrong DW (1992) Multiple enantioselective retention mechanisms on derivatized cyclodextrin gas chromatography chiral stationary phases. Analytical Chemistry 64 873-879.)...

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by GH-Av and co-workers in 1966 (113) and was based on A/-trifluoroacetyl (A/-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the tritiuoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

Gas chromatography (gc) is inferior to hplc in separating abiUty. With gc, it is better to use capillary columns and the appHcation is then limited to analysis (67). Resolution by thin layer chromatography or dc is similar to Ic, and chiral stationary phases developed for Ic can be used. However, tic has not been studied as extensively as Ic and gc. Chiral plates for analysis and preparation of micro quantities have been developed (68). 

More recendy the cis and trans isomers of the mosquito repellent CIC-4, a mixture of citroneUa isomers, have been separated by preparative hplc and bioassayed for effectiveness (23). Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazoUdine derivatives of (+)-and ( —)-citroneUal have been studied to find stmcture—activity relationships (24). Several 2-aLkyl- -acetyloxahdines have been synthesized and tested against mosquitoes, with further efforts using nmr to determine the rotational isomers of the more active N-acetyl-2,2-dimethyloxazohdine (25). 

The resolution of optically active compounds by gas chromatography with chiral phases is a well-established procedure, and the separation of Al-perfluoto-acetylated ammo acid ester enantiomers m 1967 was the first successful application of enantioselective gas-liquid chromatography [39] Ammo acids have been resolved as their A -trifluoroacetyl esters on chiral diamide phases such as N-lauroyl-L-valineferf-butylamideorAl-docosanoyl-L-valme /ez-r-butylamide [40,41,... 

A. Mosandl, U. Hener, U. Hagenauer-Hener and A. Kustertnann, Direct enantiomer separation of chiral y-lactones from food and beverages hy multidimensional gas chromatography , /. High Resolut. Chromatogr. 12 532-536 (1989). 

When the desired hydrogen uptake had been achieved, the vessel was opened, catalyst separated by filtration, and the reaction solution analysed by chiral gas chromatography (column Cydex B, 50 m, SGE Ltd). Analysis gave conversion and enantiomeric excess Enantiomeric excess is defined as IR - SI /(R+S). 

The first chiral phases introduced for gas chromatography were either amino acid esters, dipeptide, diamide or carbonyl-bis(amino acid ester) phases [721,724,756-758]. In general, these phases exhitdted poor thermal stability and are infrequently used today. Real interest and progress in chiral separations resulted from the preparation of diamide phases grafted onto a polysiloxane backbone. These phases were thermally stable and could be used to prepare efficient open tubular columns [734,756,758-762]. These phases are prepared from commercially available poly(cyano-propylmethyldimethylsiloxanes) or poly (cyanopropylmethylphenyl-... 

Capillary electrophoresis employing chiral selectors has been shown to be a useful analytical method to separate enantiomers. Conventionally, instrumental chiral separations have been achieved by gas chromatography and by high performance liquid chromatography.127 In recent years, there has been considerable activity in the separation and characterization of racemic pharmaceuticals by high performance capillary electrophoresis, with particular interest paid to using this technique in modem pharmaceutical analytical laboratories.128 130 The most frequently used chiral selectors in CE are cyclodextrins, crown ethers, chiral surfactants, bile acids, and protein-filled... 

Bordajandi, L.R., Korytar, P., De Boer, J., Gonzalez, M.J. (2005). Enantiomeric separation of chiral polychlorinated biphenyls on P-cyclodextrin capillary columns by means of heart-cut multidimensional gas chromatography and comprehensive two-dimensional gas chromatography applications to food samples. J. Sep. Sci. 28, 163-171. 

The reaction was diluted with TBME (100 mL) and stirred for 30 min. The phases were separated and once more TBME (100 mL) was added to the aqueous phase. The mixture was stirred for 10 min. The organic phases were combined and dried over Na2S04. Evaporation of the solvent yielded the cmde (5)-3-Hydroxytetrahydrothiophene-3-carbonitrile (10.26 g, 80 %) as shghtly yellow oil with 91 % ee measured by chiral gas chromatography (GC) after TMS-protection (ChirasU-Dex, 120 °C isotherm 11.9 min (5), 12.1 min (/ )). 

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