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Backbone Modification of Chirasil-Val, Part II: Introduction of a Rigid Cyclohexyl Spacer
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1995
Year
EngineeringBiochemistryNatural SciencesBackbone ModificationPolysiloxane BackboneRigid SpacerOrganic ChemistryStereoselective SynthesisChemistryRigid Cyclohexyl SpacerAsymmetric CatalysisSynthetic ChemistryEnantioselective SynthesisBiomolecular EngineeringPart IiAmino Acid Derivatives
The polysiloxane backbone of the gas chromatographic phase Chirasil-Val is modified by introducing a rigid spacer. Thus, improved shielding of the chiral moiety from the achiral polysiloxane units is achieved. The new phase, Chirasil Nova-CH, is prepared by coupling 4-exomethylen cyclohexyl carboxylic acid to L-valine tert-butylamide, followed by hydrosilylation with a copolymer containing Si-H groups. As compared with Chirasil-Nova bearing the linear spacer (CH2)3, the new phase, Chirasil-Nova-CH with a cyclohexyl spacer, shows an advantageous shortening of retention times without an apparent loss in the resolution factors for the enantiomers of amino acid derivatives.