title: Combining the enantioselectivities of L-valine diamide and permethylated beta-cyclodextrin in one gas chromatographic chiral stationary phase.
abstract: An L-valine diamide chiral selector was attached to a polysiloxane through a long hydrocarbon spacer giving rise to a chiral stationary phase (CSP), Chirasil-Val-C11. The enantioselective properties of this readily accessible diamide CSP under gas chromatographic conditions were found to be similar to that of the commercially available Chirasil-Val CSP prepared by a polymer-analogous route. A new binary CSP, Chirasil-DexVal-C11, was synthesized by means of simultaneous attachment of both the L-valine diamide and permethylated beta-cyclodextrin selectors to a polysiloxane using platinum-catalyzed hydrosilylation, thereby overcoming the immiscibility problem known for Chirasil-Val and Chirasil-Dex. This binary CSP retained both the enantioselectivity of Chirasil-Val-C11 toward alpha-amino acid derivatives and the unsurpassed enantioselectivity of Chirasil-Dex toward underivatized chiral alcohols, ketones, and hydrocarbons. Furthermore, it was shown that the presence of the cyclodextrin selector in Chirasil-Val-C11 significantly improved the enantioseparation of proline, which represented a problematic amino acid on diamide CSPs.
authors.affiliation: Institute of Organic Chemistry, University of Tübingen, Germany.
authors.forename: Pavel A
authors.initials: PA
authors.lastname: Levkin
authors.forename: Anna
authors.initials: A
authors.lastname: Levkina
authors.forename: Volker
authors.initials: V
authors.lastname: Schurig
mesh_terms: D000438:Alcohols / Q000737:chemistry; D002082:Butylamines / Q000737:chemistry; D002849:Chromatography, Gas / Q000379:methods*; D003958:Diamide / Q000737:chemistry*; D008745:Methylation; D015394:Molecular Structure; D013237:Stereoisomerism; D014633:Valine / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000438:Alcohols; D002082:Butylamines; D047392:beta-Cyclodextrins; D003958:Diamide; D014633:Valine