title: Enantiomeric separation of N-protected amino acids by non-aqueous capillary electrophoresis with dimeric forms of quinine and quinidine derivatives serving as chiral selectors.
abstract: A non-aqueous capillary electrophoretic method with quinine and tert.-butyl carbamoylated quinine as chiral selectors was developed previously for the enantioseparation of N-protected amino acids. This system was here applied as a screening tool for a fast evaluation of the chiral discrimination potential of six new dimeric forms of carbamoylated quinine and quinidine derivatives as chiral additives: 1,3-phenylene-bis(carbamoylated quinine), 1,6-hexamethylene-bis(carbamoylated quinine), 1,6-hexamethylene-bis(carbamoylated quinidine), trans-1,4-cyclohexylene-bis(carbamoylated quinine), trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylthio-dihydroquinine) and trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylsulfinyl-dihydroquinine). A series of 24 chiral acids, as various benzoyl, 3,5-dinitrobenzoyl (DNB) and 3,5-dinitrobenzyloxycarbonyl amino acid derivatives were investigated with regards to enantioselectivity employing these different dimeric chiral selectors. The composition of the background electrolyte was 12.5 mM ammonia, 100 mM octanoic acid, and 10 mM chiral selector in an ethanol-methanol (60:40, v/v) mixture and the enantioseparations were performed at 15 degrees C and in the reversed polarity mode at -25 kV. With these dimeric chiral selectors, higher enantioselectivity values, compared to those obtained with monomeric derivatives, were usually achieved, especially with the dimers containing dodecyl substituents. For example, an alpha value of 4 and a resolution value of 78 were obtained for DNB-phenylalanine, using trans-1,4-cyclohexylene-bis(carbamoylated-11-dodecylthio-dihydroquinine) as selector.
authors.affiliation: Laboratory of Drug Analysis, Scientific Institute of Public Health-Louis Pasteur, Rue Juliette Wytsman, 14, B-1050 Brussels, Belgium. veronique.piette@iph.fgov.be
authors.forename: Véronique
authors.initials: V
authors.lastname: Piette
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lindner
authors.forename: Jacques
authors.initials: J
authors.lastname: Crommen
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000302:isolation & purification; D019075:Electrophoresis, Capillary; D007202:Indicators and Reagents; D011108:Polymers / Q000737:chemistry; D011802:Quinidine / Q000737:chemistry* / Q000302:isolation & purification; D011803:Quinine / Q000737:chemistry* / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D007202:Indicators and Reagents; D011108:Polymers; D011803:Quinine; D011802:Quinidine