BACKBONE MODIFICATION OF CHIRASIL-VAL .2. INTRODUCTION OF A RIGID CYCLOHEXYL SPACER

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)3the 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. © 1995, Oxford University Press.