title: High-performance liquid chromatographic enantioseparation of unusual isoxazoline-fused 2-aminocyclopentanecarboxylic acids on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid-based chiral stationary phases.
abstract: The enantiomers of four unusual isoxazoline-fused 2-aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as chiral selector. The nature of the alcoholic modifier (MeOH, EtOH, IPA) exerted a great effect on the retention, whereas the selectivity and resolution did not change substantially. Two types of dependence of retention on alcohol content were detected: k(1) increased continuously with increasing alcohol content or a U-shaped retention curve was observed. A comparison of the chromatographic data obtained with HCOOH, AcOH, TFA, HClO(4), H(2)SO(4), or H(3)PO(4) as acidic modifier at a constant concentration demonstrated that in most cases, larger k values were obtained on the application of AcOH or HCOOH, and an increase of the acid content resulted in a decrease of retention. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes and selector. The sequence of elution of the enantiomers was determined in all cases.
authors: Institute of Pharmaceutical Chemistry, University of Szeged, Hungary.
authors: László
authors: L
authors: Sipos
authors: István
authors: I
authors: Ilisz
authors: Anita
authors: A
authors: Aranyi
authors: Zsanett
authors: Z
authors: Gecse
authors: Melinda
authors: M
authors: Nonn
authors: Ferenc
authors: F
authors: Fülöp
authors: Myung Ho
authors: MH
authors: Hyun
authors: Antal
authors: A
authors: Péter
mesh_terms: D002851:Chromatography, High Pressure Liquid; D043844:Crown Ethers / Q000737:chemistry*; D003515:Cycloleucine / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D043844:Crown Ethers; D010456:Peptides, Cyclic; D003515:Cycloleucine; C090732:18-crown-6 2,3,11,12-tetracarboxylic acid; C074972:westiellamide