title: Enantioseparation of phenylalanine analogs on a quinine-based anion-exchanger chiral stationary phase: structure and temperature effects.
abstract: Application of a cinchona alkaloid-based chiral anion-exchanger stationary phase for the direct high-performance liquid chromatographic enantioseparation of N-protected unusual phenylalanine analogs is reported. The N-benzyloxycarbonyl, N-3,5-dinitrobenzyloxycarbonyl, N-benzoyl and N-3,5-dinitrobenzoyl derivatives were well separable with high resolution. To achieve optimal separation of the enantiomers, the chromatographic conditions and temperature were varied. Linear van't Hoff plots were observed in the studied temperature range, 278-343 K, and the apparent changes in enthalpy, delta(deltaH degrees), entropy, delta(delta S degrees), and Gibbs free energy, delta(delta G degrees), were calculated. The values of the thermodynamic parameters depended on the nature of the N-acyl groups, on the structures of the compounds, and especially on the nature of the substituent on C3 of phenylalanine.
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Roland
authors.initials: R
authors.lastname: Török
authors.forename: Robert
authors.initials: R
authors.lastname: Berkecz
authors.forename: Antal
authors.initials: A
authors.lastname: Péter
mesh_terms: D000837:Anion Exchange Resins / Q000737:chemistry; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation / Q000379:methods*; D002845:Chromatography / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods*; D007202:Indicators and Reagents / Q000494:pharmacology; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000032:analysis* / Q000302:isolation & purification*; D011803:Quinine / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000837:Anion Exchange Resins; D007202:Indicators and Reagents; D010649:Phenylalanine; D011803:Quinine