Chiral Polysiloxanes Research Articles

Direct resolution of enantiomeric diols by capillary gas chromatography on a chiral polysiloxane derived from (R,R)-tartramide

Etude du dedoublement optique des composes diols, aliphatiques et alicycliques sans avoir subi de derivatisations, sur une nouvelle phase polymerique chirale

Chiral polysiloxanes derived from (R,R)-tartramide for the gas chromatographic separation of enantiomers

Chiral polysiloxanes derived from (R,R)-tartramide for the gas chromatographic separation of enantiomers

Chiral stationary phases for capillary gas chromatography: Towards higher selectivity and stability

AbstractThermal stability and enantioselectivity of chiral polysiloxane stationary phases for gas chromatography depend upon the composition and purity of the polymer matrix, its functional groups, the chiral selector, and the pretreatment of the inner surface of the capillary. Under proper conditions, narrow‐bore capillaries can be prepared which may be used up to 300 °C for short times. Crosslinking of the phases is achieved by heating.

Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part II: Heptakis(3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐ß‐cyclodextrin

AbstractHeptakis (3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐ß‐cyclodextrin is used as a chiral stationary phase in capillary gas chromatography. High enantioselectivity towards trifluoro‐acetylated α and β‐chiral amines, amino alcohols, α‐ and β‐amino acid esters, and cyclic trans‐diols is observed. In contrast to chiral polysiloxane phases, where hydrogen bonding interaction is essential for enantiomer separation, in cyclodextrins inclusion properties contribute to enantioselectivity. This can be concluded from the separation of N‐alkylated amino compounds. The new chiral stationary phase exhibits a wide operating temperature range and is stable above 200°C.

Enantiomeric analysis by gas chromatography on chiral polysiloxanes

Abstract Chemical modification of commercially available cyanoalkyl polysiloxanes provided polymers with carboxylic side groups, which were derivatized with chiral compounds. The resultant chiral polymers were used as stationary phases for the separation of enantiomers by gas chromatography (GC), and their stereoselectivity was studied in relation to (i) the concentration and type of chiral moiety and (ii) the length of the side chain spacer.

Capillary Gas Chromatographic Analysis of Amino Acids by Enantiomer Labeling

The optical isomers of amino acids can be easily separated by gas chromatography using capillary columns coated with the chiral polysiloxane peptide, Chirasil-Val. Quantitative trace amino acid analysis in complex mixtures such as biological fluids, sea water, or protein hydrolysates can be achieved by enantiomer labeling: The D-amino acid enantiomers, which do not occur naturally, are added to the sample prior to analysis as internal standards. Because the D-enantiomers show the same physical and chemical properties as the natural L-enantiomers, they are ideal standard references. In routine analysis, the derivatization is achieved with a new automated derivatization robot. The D-standard serves as overall internal standard for the whole analytical procedure from sample enrichment to derivatization, chromatography, and response of the detector.

New chiral polysiloxanes prepared from derivatives of (+)- or (-)-2-phenyl-3-butehoic acid, (r)-l-hepten-3-ol and (r)-l-cyclohexyl-2-propen-1-ol

A series of new polysiloxanes containing chiral side groups has been prepared. These polymers were prepared by hydrosilylating chiral alkene derivatives onto polyhydromethylsiloxane. The alkene derivatives were prepared from (+) or (-)-2-phenyl-3-butenoic acid, (R)-1-hepten-3-ol and (R)-1-cyclohexyl-2-propen-1-ol. Polysiloxanes containing racemic substituents were also prepared fron derivatives of racemic 3-buten-2-ol. The polysiloxanes containing biphenyl carboxylate derivatives (11a–13a) had liquid crystalline properties. These polymers were prepared for use as stationary phases for capillary gas and supercritical fluid chromatography.

Enantioselective Capillary Gas Chromatography of Proline and Congeners

AbstractA base line enantiomer separation of esters of N‐pivaloyl Pro and some congeners is obtained on commercial OV‐225 and Chirasil‐Val chiral polysiloxane phases.

Gas chromatographic enantiomer separation of chiral ketones — Order of elution and configurational stability of oxime derivatives

Oximes of chiral ketones can be separated into enantiomers by capillary gas chromatography on the chiral polysiloxanes XE-60-L-valine-(S)- or (R)-α-phenylethylamide. Usually predominantly E-isomers are formed and are better separated than Z-isomers. From time-dependent gas chromatographic measurements it can be concluded that the oximes are configurationally stable and that racemization during oxime formation is negligible. The order of elution of enantiomers depends on the structure of the ketone and is different for aliphatic and alicyclic compounds.

Phosgene —a versatile reagent for enantiomer separation by capillary gas chromatography

Phosgene has been used to form cyclic derivatives of chiral diols, α-hydroxy acids, N-methylamino acids and other di- and trifunctional compounds and the enantiomers then separated by gas chromatography on the chiral polysiloxane phase XE-60— L-valine—( R)-α-phenylethylamide. In this way phosgene can supplement the isocyanates as a versatile reagent for enantiomer separation.

Chirale Erkennung von Naturstoffen an optisch aktiven Polysiloxanen Chiral Recognition of Natural Products on Optically Active Polysiloxanes

Abstract Polysiloxanes with chiral peptide side chains have been synthesized and used as stationary phases in gas chromatography. With these phases amino acid enantiomers can be separated as N-acyl esters. Due to temperature stability up to 230 °C all protein amino acids can be separated and the racemization of synthetic biologically active peptides controlled. The phases can be used to assign the absolute configuration of amino acids. A variety of other classes of compounds can be separated into their enantiomers using the chiral polysiloxanes, like hydroxy acids, sulfoxides, phosphorous compounds, glycols, atrop isomers, amines and alcohols. Various applications of these phases are described including investigations of enantiomer selectivity in nature.

Chiral Polysiloxanes for Resolution of Optical Antipodes

The imparting of natural enantiomer selectivity to synthetic polymers is a matter of topical interest. A polymeric organosiloxane containing an amino acid as a chiral center has now been synthesized as an “artificial receptor”. This product can be used, inter alia, for enantiomer analysis by gas chromatography, and serves as model for studies on the biological action of enantiomeric substrates.