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Labíková M, Svoboda J, Tůma J, Lindner W, Kohout M. Chiral recognition without π-π-interactions: Highly efficient chiral strong cation exchangers lacking an aromatic unit in the molecular structure. J Chromatogr A 2024; 1719:464729. [PMID: 38387150 DOI: 10.1016/j.chroma.2024.464729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/07/2024] [Accepted: 02/09/2024] [Indexed: 02/24/2024]
Abstract
Current state-of-the-art chiral stationary phases (CSPs) enable chiral resolution of almost any racemic mixture of choice. The exceptions represent ionizable and ionized substances that fail at any attempts to resolve on commercially available CSPs. These compounds, however, can be efficiently separated on chiral ion exchangers. Commercially available Cinchona alkaloids-based chiral weak ion-exchangers are typically used for chiral resolution of organic acids, while zwitterion ion-exchangers are efficient in the resolution of acids, bases, and zwitterions. The latter possess in their structure a cation exchange unit, which alone can serve as a cornerstone of chiral strong cation exchangers facilitating chiral separation of various basic racemic mixtures. Although chiral strong cation exchangers (cSCX) are efficient CSPs, their structural variations have not been thoroughly studied so far. It was assumed that the mechanism of chiral recognition of basic compounds by cSCX is based predominantly on π-π-interactions, hydrogen bonding and steric interactions (CSP I). To verify this assumption, we aimed in our study on the design and synthesis of cSCX first lacking lateral polar substituents on the aromatic unit in the selector's structure (CSP II), and second, to replace the aromatic unit by a cyclohexane ring (CSP III and IV), thereby to omit completely the π-π-interactions. We hypothesized that this structural change should lead to a partial or complete loss of enantiorecognition power of the selectors. Surprisingly, the non-aromatic cSCXs have shown chiral recognition capability comparable to that of previously described chiral cation exchange-type CSPs: from 16 analytes screened, 11 analytes were baseline resolved and 5 partially resolved on CSP I, while non-aromatic CSP III resolved 10 analytes baseline and 6 partially. We discuss the structural motifs of the known cSCX and the novel non-aromatic selectors in a relationship with their chromatographic performance using a set of basic analytes. Moreover, we present a theory of an effective chiral recognition mechanism by two novel non-aromatic cSCXs based on the chromatographic results and quantum mechanical calculations.
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Affiliation(s)
- Magdaléna Labíková
- Department of Organic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Jiří Svoboda
- Department of Organic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Jiří Tůma
- Department of Organic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
| | - Wolfgang Lindner
- Institute of Analytical Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria
| | - Michal Kohout
- Department of Organic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic.
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Kozlov O, Záhoráková D, Armstrong DW, Gondová T. Enantiomeric separation of bupropion by liquid chromatography on derivatized cyclofructan chiral stationary phase. Chirality 2022; 34:1311-1319. [DOI: 10.1002/chir.23496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 07/12/2022] [Accepted: 07/15/2022] [Indexed: 11/12/2022]
Affiliation(s)
- Oleksandr Kozlov
- Department of Analytical Chemistry, Faculty of Science P.J. Šafárik University Košice Slovak Republic
- Department of Chemistry, Faculty of Science University of Hradec Králové Hradec Králové Czech Republic
| | - Daniela Záhoráková
- Department of Analytical Chemistry, Faculty of Science P.J. Šafárik University Košice Slovak Republic
| | - Daniel W. Armstrong
- Department of Chemistry and Biochemistry University of Texas at Arlington Arlington Texas USA
| | - Taťána Gondová
- Department of Analytical Chemistry, Faculty of Science P.J. Šafárik University Košice Slovak Republic
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Tanács D, Bajtai A, Berkecz R, Forró E, Fülöp F, Lindner W, Péter A, Ilisz I. Cinchona-alkaloid-based zwitterionic chiral stationary phases as potential tools for high-performance liquid chromatographic enantioseparation of cationic compounds of pharmaceutical relevance. J Sep Sci 2021; 44:2735-2743. [PMID: 33999502 DOI: 10.1002/jssc.202100264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/07/2021] [Accepted: 05/10/2021] [Indexed: 11/11/2022]
Abstract
Enantiomers of cationic compounds of pharmaceutical relevance, namely tetrahydro-ß-carboline and 1,2,3,4-tetrahydroisoquinoline analogs, were separated by high-performance liquid chromatography. Separations were performed on Cinchona-alkaloid-based zwitterionic ion exchanger type chiral stationary phases applied as cation exchangers using mixtures of methanol and acetonitrile or tetrahydrofuran as bulk solvent components containing triethylammonium acetate or ammonium acetate as organic salt additives. On the zwitterionic ZWIX(+) and ZWIX(-) columns investigated, retention and enantioseparation of the studied basic analytes were influenced by the nature and concentration of the organic components of the mobile phase. The effect of organic salt additives on the retention behavior of the studied analytes can be described by the stoichiometric displacement model related to the counterion concentration. Investigations on the structure-retention relationships were performed applying different mobile phase systems for the two types of cationic analytes. For the thermodynamic characterization, parameters such as changes in standard enthalpy (Δ(ΔH°)), entropy (Δ(ΔS°)), and free energy (Δ(ΔG°)) were calculated on the basis of van't Hoff plots derived from the ln α versus 1/T curves. In most cases, enthalpy-driven enantioseparations were observed, with a consistent dependence of the calculated thermodynamic parameters on the mobile phase composition. Elution sequences of the studied compounds were determined in all cases.
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Affiliation(s)
- Dániel Tanács
- Institute of Pharmaceutical Analysis, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Attila Bajtai
- Institute of Pharmaceutical Analysis, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Róbert Berkecz
- Institute of Pharmaceutical Analysis, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Enikő Forró
- Institute of Pharmaceutical Chemistry, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Ferenc Fülöp
- Institute of Pharmaceutical Chemistry, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Wolfgang Lindner
- Department of Analytical Chemistry, University of Vienna, Vienna, Austria
| | - Antal Péter
- Institute of Pharmaceutical Analysis, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - István Ilisz
- Institute of Pharmaceutical Analysis, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
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High-performance liquid chromatographic evaluation of strong cation exchanger-based chiral stationary phases focusing on stationary phase characteristics and mobile phase effects employing enantiomers of tetrahydro-ß-carboline and 1,2,3,4-tetrahydroisoquinoline analogs. J Chromatogr A 2021; 1644:462121. [PMID: 33845425 DOI: 10.1016/j.chroma.2021.462121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 03/25/2021] [Accepted: 03/28/2021] [Indexed: 11/22/2022]
Abstract
In this study, we present results obtained on the enantioseparation of some cationic compounds of pharmaceutical relevance, namely tetrahydro-ß-carboline and 1,2,3,4-tetrahydroisoquinoline analogs. In high-performance liquid chromatography, chiral stationary phases (CSPs) based on strong cation exchanger were employed using mixtures of methanol and acetonitrile or tetrahydrofuran as mobile phase systems with organic salt additives. Through the variation of the applied chromatographic conditions, the focus has been placed on the study of retention and enantioselectivity characteristics as well as elution order. Retention behavior of the studied analytes could be described by the stoichiometric displacement model related to the counter-ion effect of ammonium salts as mobile phase additives. For the thermodynamic characterization parameters, such as changes in standard enthalpy Δ(ΔH°), entropy Δ(ΔS°), and free energy Δ(ΔG°), were calculated on the basis of van't Hoff plots derived from the ln α vs. 1/T curves. In all cases, enthalpy-driven enantioseparations were observed with a slight, but consistent dependence of the calculated thermodynamic parameters on the eluent composition. Elution sequences of the studied compounds were determined in all cases. They were found to be opposite on the enantiomeric stationary phases and they were not affected by either the temperature or the eluent composition.
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Enantioselective separation of zopiclone on immobilized polysaccharide chiral stationary phase by HPLC: Method development and validation. J Pharm Biomed Anal 2020; 190:113549. [DOI: 10.1016/j.jpba.2020.113549] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 08/04/2020] [Accepted: 08/06/2020] [Indexed: 01/30/2023]
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Liquid chromatographic chiral recognition of phytoalexins on immobilized polysaccharides chiral stationary phases. Unusual temperature behavior. J Chromatogr A 2019; 1601:178-188. [PMID: 31056269 DOI: 10.1016/j.chroma.2019.04.070] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/26/2019] [Accepted: 04/27/2019] [Indexed: 12/24/2022]
Abstract
Three immobilized polysaccharide chiral stationary phases, Chiralpak IA, Chiralpak IB and Chiralpak IC, were used for the study of enantioseparation of 36 derivatives of natural indole phytoalexins, in most cases bioactive, including racemic spirobrassinin, 1-methoxyspirobrassinin and 1-methoxyspirobrassinol methyl ether. Almost all analytes were baseline resolved at least on two different polysaccharide columns in normal phase mode. The effects of mobile phase composition, the analyte structure and the column temperature on the retention and enantioseparation were investigated. Evaluation of the corresponding thermodynamic parameters using van´t Hoff plots (ln k versus 1/T) in the temperature range -15 to 50 °C indicated that separations were enthalpy controlled in most cases, but some entropy controlled separations were also observed. Moreover, unusual phenomenon, an increase retention with increasing temperature accompanied with increased resolution was observed on the Chiralpak IC column. The elution order of enantiomers was determined in some cases and reversed elution order was also observed.
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Lajkó G, Orosz T, Ugrai I, Szakonyi Z, Fülöp F, Lindner W, Péter A, Ilisz I. Liquid chromatographic enantioseparation of limonene-based carbocyclic β-amino acids on zwitterionic Cinchona
alkaloid-based chiral stationary phases. J Sep Sci 2017. [DOI: 10.1002/jssc.201700450] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Gyula Lajkó
- Department of Inorganic and Analytical Chemistry; University of Szeged; Szeged Hungary
- Institute of Pharmaceutical Chemistry; University of Szeged; Szeged Hungary
| | - Tímea Orosz
- Department of Inorganic and Analytical Chemistry; University of Szeged; Szeged Hungary
| | - Imre Ugrai
- Institute of Pharmaceutical Chemistry; University of Szeged; Szeged Hungary
| | - Zsolt Szakonyi
- Institute of Pharmaceutical Chemistry; University of Szeged; Szeged Hungary
| | - Ferenc Fülöp
- Institute of Pharmaceutical Chemistry; University of Szeged; Szeged Hungary
| | - Wolfgang Lindner
- Department of Analytical Chemistry; University of Vienna; Vienna Austria
| | - Antal Péter
- Department of Inorganic and Analytical Chemistry; University of Szeged; Szeged Hungary
| | - István Ilisz
- Department of Inorganic and Analytical Chemistry; University of Szeged; Szeged Hungary
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Orosz T, Grecsó N, Lajkó G, Szakonyi Z, Fülöp F, Armstrong DW, Ilisz I, Péter A. Liquid chromatographic enantioseparation of carbocyclic β-amino acids possessing limonene skeleton on macrocyclic glycopeptide-based chiral stationary phases. J Pharm Biomed Anal 2017; 145:119-126. [PMID: 28654779 DOI: 10.1016/j.jpba.2017.06.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/01/2017] [Accepted: 06/06/2017] [Indexed: 10/19/2022]
Abstract
Polar-ionic and reversed-phase high-performance liquid chromatographic separations of limonene-based cyclic β-amino acid enantiomers were carried out by using macrocyclic glycopeptide-based chiral selectors applying Chirobiotic T, TAG and R columns. The effects of additives, concentration of the co- and counter-ions and the temperature in polar-ionic mobile phase systems were studied. The influence of pH, MeOH content and alcohol additives were investigated in the reversed-phase mode. The difference in the change in standard enthalpy Δ(ΔH°), entropy Δ(ΔS°), and free energy Δ(ΔG°) was calculated from the linear van't Hoff plots derived from the ln α vs 1/T curves in the temperature range 5-40°C. Unusual temperature behavior was observed on Chirobiotic TAG for most of the analytes: decreased retention times were accompanied with increased separation factors with increasing temperature, and separation was entropically-driven. For two of the studied analytes enthalpically-driven enantioseparations were observed. The elution sequence was determined in all cases, but no general rule could be established.
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Affiliation(s)
- Tímea Orosz
- Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7, Hungary
| | - Nóra Grecsó
- Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7, Hungary; Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6, Hungary
| | - Gyula Lajkó
- Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7, Hungary; Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6, Hungary
| | - Zsolt Szakonyi
- Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6, Hungary
| | - Ferenc Fülöp
- Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6, Hungary
| | - Daniel W Armstrong
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019-0065, USA
| | - István Ilisz
- Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7, Hungary.
| | - Antal Péter
- Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7, Hungary
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