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Dalvano BE, Wenzel TJ. Sulfated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.tetasy.2017.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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2
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Puentes CM, Wenzel TJ. Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds. Beilstein J Org Chem 2017; 13:43-53. [PMID: 28179947 PMCID: PMC5238554 DOI: 10.3762/bjoc.13.6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/22/2016] [Indexed: 11/27/2022] Open
Abstract
The utility of phosphated α-, β- and γ-cyclodextrins as water-soluble chiral NMR solvating agents for cationic substrates is described. Two sets of phosphated cyclodextrins, one with degrees of substitution in the 2–6 range, the other with degrees of substitution in the 6–10 range, are examined. Results with 33 water-soluble cationic substrates are reported. We also explored the possibility that the addition of paramagnetic lanthanide ions such as praseodymium(III) and ytterbium(III) further enhances the enantiomeric differentiation in the NMR spectra. The chiral differentiation with the phosphated cyclodextrins is compared to prior results obtained with anionic carboxymethylated cyclodextrins. There are a number of examples where a larger differentiation is observed with the phosphated cyclodextrins.
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Affiliation(s)
| | - Thomas J Wenzel
- Department of Chemistry, Bates College, Lewiston, Maine 04240 USA
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3
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Pham NH, Wenzel TJ. A water-soluble calix[4]resorcinarene with L-pipecolinic acid groups as a chiral NMR solvating agent. Chirality 2012; 24:193-200. [DOI: 10.1002/chir.21979] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/19/2011] [Indexed: 11/09/2022]
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4
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Pham NH, Wenzel TJ. A sulfonated calix[4]resorcinarene with l-pipecolinic acid groups as a water-soluble chiral NMR solvating agent. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.tetasy.2011.08.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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5
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Pham NH, Wenzel TJ. A sulfonated calix[4]resorcinarene with α-methyl-l-prolinylmethyl groups as a water-soluble chiral NMR solvating agent. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.tetasy.2011.04.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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6
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Xiao Y, Wang Y, Ong TT, Ge L, Tan SN, Young DJ, Tan TTY, Ng SC. Chiral capillary electrophoresis with cationic pyrrolidinium-β-cyclodextrin derivatives as chiral selectors. J Sep Sci 2010; 33:1797-805. [DOI: 10.1002/jssc.200900732] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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7
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Berta R, Szakács Z, Babják M, Gazdag M. The Role of Temperature in Enantioseparation of Norgestrel with Native Cyclodextrins: A Combined LC and NMR Study. Chromatographia 2010. [DOI: 10.1365/s10337-010-1511-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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8
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O'Farrell CM, Hagan KA, Wenzel TJ. Water-soluble calix[4]resorcinarenes as chiral NMR solvating agents for bicyclic aromatic compounds. Chirality 2009; 21:911-21. [DOI: 10.1002/chir.20688] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Hagan KA, O'Farrell CM, Wenzel TJ. Water-Soluble Calix[4]resorcinarenes with Hydroxyproline Groups as Chiral NMR Solvating Agents for Phenyl- and Pyridyl-Containing Compounds. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900674] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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10
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Sun P, Macdonnell FM, Armstrong DW. Enantioselective Host-Guest Complexation of Ru(II) trisdiimine complexes using neutral and anionic derivatized cyclodextrins. Inorganica Chim Acta 2009; 362:3073-3078. [PMID: 20161587 DOI: 10.1016/j.ica.2009.02.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Enantioselective host-guest complexation between five racemic Ru(II) trisdiimine complexes and eight derivatized cyclodextrins (CDs) has been examined by NMR techniques. The appearance of non-equivalent complexation-induced shifts of between the Δ and Λ-enantionomers of the Ru(II) trisdiimine complexes and derivatized CDs is readily observed by NMR. In particular, sulfobutyl ether-β-cyclodextrin sodium salt (SBE-β-CD), R-naphtylethyl carbamate β-cyclodextrin (RN-β-CD), and S-naphtylethyl carbamate β-cyclodextrin (SN-β-CD) showed good enantiodiscrimination for all five Ru complexes examined, which indicates that aromatic and anionic derivatizing groups are beneficial for chiral recognition. The complexation stoichiometry between SBE-β-CD and [Ru(phen)(3)](2+) was found to be 1: 1 and binding constants reveal that Λ-[Ru(phen)(3)](2+) binds more strongly to SBE-β-CD than the Δ-enantiomer. Correlations between this NMR method and separative techniques based on CDs as chiral discriminating agents (i.e., selectors) are discussed in detail.
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Affiliation(s)
- Ping Sun
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, TX 76019, USA
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11
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Water-soluble calix[4]resorcinarenes as chiral NMR solvating agents for phenyl-containing compounds. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.tetasy.2008.07.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Gao Y, Luo Y, Qin J, Lin B. A multichannel electrophoresis microchip platform for rapid chiral selector screening. Electrophoresis 2008; 29:1918-23. [DOI: 10.1002/elps.200700384] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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13
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Dignam CF, Randall LA, Blacken RD, Cunningham PR, Lester SKG, Brown MJ, French SC, Aniagyei SE, Wenzel TJ. Carboxymethylated cyclodextrin derivatives as chiral NMR discriminating agents. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2006.04.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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14
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Smith KJ, Wilcox JD, Mirick GE, Wacker LS, Ryan NS, Vensel DA, Readling R, Domush HL, Amonoo EP, Shariff SS, Wenzel TJ. Calix[4]arene, calix[4]resorcarene, and cyclodextrin derivatives and their lanthanide complexes as chiral NMR shift reagents. Chirality 2004; 15 Suppl:S150-8. [PMID: 12884386 DOI: 10.1002/chir.10254] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Calix[4]arenes, calix[4]resorcarenes, and anionic cyclodextrin derivatives were examined as chiral NMR solvating agents. The calix[4]arenes were prepared by attachment of amino acids through the hydroxyl groups of the phenol rings. Chloroform-, methanol-, and water-soluble derivatives were prepared and tested with a range of substrates. Chloroform-soluble chiral calix[4]resorcarenes were prepared by attachment of chiral primary and secondary amines and examined in NMR applications with a variety of substrates. Sulfated and carboxymethylated beta-cyclodextrin are effective at causing enantiomeric discrimination in the (1)H NMR spectra of organic cations. Lanthanide ions associate at the carboxymethyl groups and cause sizeable shifts and enhancements in enantiomeric discrimination in the spectra of organic cations. The enhancements caused by the lanthanide ion are large enough that much lower concentrations of the cyclodextrin can be used as compared to conventional analyses.
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Affiliation(s)
- Kristin J Smith
- Department of Chemistry, Bates College, Lewiston, Maine, USA
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15
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Sulfated and carboxymethylated cyclodextrins and their lanthanide complexes as chiral NMR discriminating agents. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/j.tetasy.2003.07.019] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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16
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Anczewski W, Dodziuk H, Ejchart A. Manifestation of chiral recognition of camphor enantiomers by alpha-cyclodextrin in longitudinal and transverse relaxation rates of the corresponding 1:2 complexes and determination of the orientation of the guest inside the host capsule. Chirality 2003; 15:654-9. [PMID: 12840832 DOI: 10.1002/chir.10277] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The 1:2 complexes of camphor enantiomers with alpha-cyclodextrin in (2)H(2)O manifest differences in longitudinal and transverse relaxation rates of camphor methyl protons owing to chiral recognition. The relaxation data obtained at two magnetic fields were quantitatively analyzed using the model of anisotropic overall tumbling with internal motion. In experimental conditions (guest-to-host ratio = 1:20, T = 300.6K), all camphor molecules are complexed. The complexes are not rigid but the rotational diffusion of camphor enantiomers embedded inside the capsules formed by two alpha-cyclodextrin hosts is well outside the extreme narrowing region. Both differences in the anisotropic overall tumbling and internal rotation of all methyl groups participate in enantiomeric differentiation of the relaxation rates. Anisotropic tumbling of camphor molecules provides information on the orientation of the guest in the host capsule that for the complex under study could not be obtained by other methods.
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17
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Guo L, Lin SJ, Yang YF, Qi L, Wang MX, Chen Y. Fast enantioseparation of arylglycine amides by capillary electrophoresis with highly sulfated-beta-cyclodextrin as a chiral selector. J Chromatogr A 2003; 998:221-8. [PMID: 12862386 DOI: 10.1016/s0021-9673(03)00653-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nine racemic arylglycine amides were synthesized and successfully enantioseparated by capillary electrophoresis (CE) using highly sulfated beta-cyclodextrin (HS-beta-CD) as a chiral selector. Baseline enantioseparation of the analytes was obtained around neutral pH but not in the acidic conditions that are commonly used. HS-beta-CD content, buffer pH, type and concentration, and organic modifier concentration were studied and optimized for fast and efficient separation. A chiral CE separation system composed of 1.5% (w/v) HS-beta-CD, 0 to 10% (v/v) methanol and 20 mM 3-(N-morpholino)propanesulfonic acid at pH 6.5 was shown suitable for baseline enantioseparation of the mentioned amides within 6 min, including simultaneous enantioseparation of three positional isomer series (methyl-, methoxyl or chloro-substituted). By using this system, D-enantiomers migrated ahead of the L-enantiomers and the enantiomeric resolution order of arylglycine amides was more or less parallel to the pK(a), order of the analytes.
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Affiliation(s)
- Lei Guo
- Laboratory of Chemical Biology, Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, P.O. Box 2709, Beijing 100080, People's Republic of China
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18
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Beraldo H, Sinisterra RD, Teixeira LR, Vieira RP, Doretto MC. An effective anticonvulsant prepared following a host-guest strategy that uses hydroxypropyl-beta-cyclodextrin and benzaldehyde semicarbazone. Biochem Biophys Res Commun 2002; 296:241-6. [PMID: 12163008 DOI: 10.1016/s0006-291x(02)00865-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The convulsions of approximately 25% of epileptics are inadequately controlled by currently available medication; therefore the preparation of new antiepileptic drugs is of great interest. Aryl semicarbazones can be considered a new class of compounds presenting anticonvulsant activity. In addition, they can be orally administered and are more active as anticonvulsants than mephenytoin or phenobarbital. However, one disadvantage of these compounds is their low water solubility. As a strategy to circumvent this problem, a 1:1 inclusion compound of benzaldehyde semicarbazone (BS) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was prepared and characterized. The anticonvulsant activities of the free semicarbazone and of the inclusion compound were evaluated in rats using the maximum electroshock and audiogenic seizures screenings. In both tests the minimum dose of compound necessary to produce activity decreases from 100mg/kg for the free semicarbazone to 35 mg/kg for the inclusion compound, indicating a significant increase in the bio-availability of the drug.
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Affiliation(s)
- Heloisa Beraldo
- Departamento de Química, Universidade Federal de Minas Gerais, MG, Belo Horizonte, Brazil.
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19
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Tárkányi G. Quantitative approach for the screening of cyclodextrins by nuclear magnetic resonance spectroscopy in support of chiral separations in liquid chromatography and capillary electrophoresis enantioseparation of norgestrel with alpha-, beta- and gamma-cyclodextrins. J Chromatogr A 2002; 961:257-76. [PMID: 12184623 DOI: 10.1016/s0021-9673(02)00429-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A quantitative NMR approach is proposed for the screening of cyclodextrins with regard to their enantioselectivity as chiral mobile phase additives in column reversed-phase chromatography and capillary electrophoresis. Similarities and differences between the mechanism of enantiomeric peak-separation in NMR and HPLC and CE are interpreted. The affinity of d-norgestrel to bind to (alpha-, beta-, gammay-) cyclodextrins in aqueous solution was quantified and compared by determining the association constants from chemical shift data. The association constant of l-norgestrel was estimated from titration of the racemate. Differences between the apparent association constants of the enantiomerically pure drug and the racemate are discussed from the point of view of enantiomeric competition for the cyclodextrin. The apparent association constants and chiral selectivities determined by 'H NMR for dl-norgestrell/gamma-CD system at various water-methanol ratios are correlated with the corresponding chromatographic results found in the literature. The pitfalls of previously proposed screening methods based on comparison of chemical shift differences with separation parameters are discussed.
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Affiliation(s)
- Gábor Tárkányi
- Spectroscopic Research Division, Gedeon Richter Ltd, Budapest, Hungary.
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20
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Wedig M, Laug S, Christians T, Thunhorst M, Holzgrabe U. Do we know the mechanism of chiral recognition between cyclodextrins and analytes? J Pharm Biomed Anal 2002; 27:531-40. [PMID: 11755754 DOI: 10.1016/s0731-7085(01)00579-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The resolution of chiral phenethylamine analogue compounds were studied in presence of single-isomer neutral and negatively charged cyclodextrins (CDs) by means of capillary electrophoresis (CE) and NMR spectroscopy. Whereas the native beta-CD and heptakis(2-N,N-dimethylcarbamoyl)beta-cyclodextrin were not able to separate the racemates of four ephedrine derivatives studied, heptakis(2,3-O-diacetyl)beta-cyclodextrin and especially heptakis(2,3-O-diacetyl-6-sulfo)beta-cyclodextrin could resolve all four pairs of enantiomers in one run. UV and NMR spectroscopic measurements revealed various kinds of complexes of phenethylamines with the CDs. Either defined inclusion complexes or manifold complexes which are mostly characterized by an attachment of the analyte to the outside of the CD cavity were found. No correlation between the kind of complexation and the resolution observed by means of CE could be found.
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Affiliation(s)
- M Wedig
- Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, D-97074 Wurzburg, Germany
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21
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Abstract
Chiral drugs, agrochemicals, food additives and fragrances represent classes of compounds with high economic and scientific potential. First the present implications of their chiral nature and necessity of separating enantiomers are summarised in this article. In the following a brief overview of the actual approaches to perform enantioseparations at analytical and preparative scale is given. Challenging aspects of these strategies, such as problems associated with data management, choice of suitable chiral selectors for given enantioseparations and enhanced understanding of the underlying chiral recognition principles, are discussed. Alternatives capable of meeting the requirements of industrial processes, in terms of productivity, cost-effectiveness and environmental issues (e.g., enantioselective membranes) are critically reviewed. The impact of combinatorial methodologies on faster and more effective development and optimisation of novel chiral selectors is outlined. Finally, the merits and limitations of most recent trends in discrimination of enantiomers, including advances in the fields of sensors, microanalysis systems, chiroptical methods and chemical force microscopy are evaluated.
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Affiliation(s)
- N M Maier
- Institute of Analytical Chemistry, University of Vienna, Austria
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22
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Fanali S. Enantioselective determination by capillary electrophoresis with cyclodextrins as chiral selectors. J Chromatogr A 2000; 875:89-122. [PMID: 10839140 DOI: 10.1016/s0021-9673(99)01309-6] [Citation(s) in RCA: 340] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
This review surveys the separation of enantiomers by capillary electrophoresis using cyclodextrins as chiral selector. Cyclodextrins or their derivatives have been widely employed for the direct chiral resolution of a wide number of enantiomers, mainly of pharmaceutical interest, selected examples are reported in the tables. For method optimisation, several parameters influencing the enantioresolution, e.g., cyclodextrin type and concentration, buffer pH and composition, presence of organic solvents or complexing additives in the buffer were considered and discussed. Finally, selected applications to real samples such as pharmaceutical formulations, biological and medical samples are also discussed.
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Affiliation(s)
- S Fanali
- Istituto di Cromatografia del C.N.R., Area della Ricerca di Roma, Monterotondo Scalo (Rome), Italy.
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Wenzel TJ, Miles RD, Zomlefer K, Frederique DE, Roan MA, Troughton JS, Pond BV, Colby AL. Dysprosium(III)-diethylenetriaminepentaacetate complexes of aminocyclodextrins as chiral NMR shift reagents. Chirality 2000; 12:30-7. [PMID: 10602264 DOI: 10.1002/(sici)1520-636x(2000)12:1<30::aid-chir6>3.0.co;2-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A metal chelating ligand is bonded to alpha-, beta-, and gamma-cyclodextrin by the reaction of diethylenetraminepentaacetic dianhydride with the corresponding 6-mono- and 2-mono(amine)cyclodextrin. Adding Dy(III) to the cyclodextrin derivatives causes shifts in the (1)H-NMR spectra of substrates such as propranolol, tryptophan, aspartame, carbinoxamine, pheniramine, doxylamine, and 1-anilino-8-naphthalenesulfonate. The Dy(III)-induced shifts enhance the enantiomeric resolution in the NMR spectra of several substrates. Enhancements in enantiomeric resolution using cyclodextrin derivatives with the amine tether are compared to previously described compounds in which the chelating ligand is attached through an ethylenediamine tether. In general, the Dy(III) complex of the 6-beta-derivative with the amine tether is a more effective chiral resolving agent than the complex with the ethylenediamine tether. The opposite trend is observed with the 2-beta-derivatives. The presence of the chelating ligand in the 2-beta-derivative hinders certain substrates from entering the cavity. For cationic substrates, evidence suggests that a cooperative association involving inclusion in the cavity and association with the Dy(III) unit occurs. Enhancements in enantiomeric resolution in the spectrum of tryptophan are greater for the secondary alpha- and gamma-derivatives than the beta-derivative.
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Affiliation(s)
- T J Wenzel
- Department of Chemistry, Bates College, Lewiston, Maine 04240, USA
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Růžička J, Streinz L, Šaman D, Havlas Z, Wimmer Z, Zarevúcka M, Koutek B, Lešetický L. Chlorofluoroacetic Acid as a Highly Versatile Derivatizing Agent: Assignment of Stereochemistry to Esters of Chiral Alcohols. ACTA ACUST UNITED AC 2000. [DOI: 10.1135/cccc20000695] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Stereochemistry of a series of diastereomeric esters obtained from chiral alcohols 1a-21a by derivatization with (S)- or (R)-chlorofluoroacetic acid was correlated with their LC and GC separation (∆tr) and NMR resolution (∆δ). Both the chromatographic and NMR spectral behavior of respective diastereomers was found to follow systematic rules reflecting their steric arrangement. Moreover, identical conformations of the esters seem to be preferred in solution as well as in the chromatographic processes. Reasons underlying this behavior are discussed.
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25
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Galaverna G, Corradini R, Dossena A, Marchelli R. Histamine-modified cationic beta-cyclodextrins as chiral selectors for the enantiomeric separation of hydroxy acids and carboxylic acids by capillary electrophoresis. Electrophoresis 1999; 20:2619-29. [PMID: 10532327 DOI: 10.1002/(sici)1522-2683(19990901)20:13<2619::aid-elps2619>3.0.co;2-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The enantiomeric separation of alpha-hydroxy acids and carboxylic acids was successfully performed by using 6-deoxy-6-N-histamino-beta-cyclodextrin (CD-hm), a monosubstituted positively charged beta-cyclodextrin (beta-CD) bearing a histamine moiety linked to the C6 of a glucose unit in the upper CD rim via the amino group. Good results were obtained at a low selector concentration (1 mM). The number of positive charges on the upper rim may be modulated as a function of pH, because of the different pKa of the amino and the imidazolyl groups, and was found to affect both the enantioselectivity and resolution factors. With the analogous 6-deoxy-[4-(2-aminoethyl)imidazolyl]-beta-cyclodextrin (CD-mh) bearing the histamine moiety linked to the C6 via the imidazolyl group, very poor results were obtained, showing that the proximity of the positive charge to the cavity plays an important role in the enantiomeric recognition. The complexation mode was studied by electrospray ionization-mass spectrometry (ESI-MS) and two-dimensional nuclear magnetic resonance (2-D NMR) ROESY experiments: the recognition model is consistent with an inclusion complexation of the aromatic ring of the analyte within the CD cavity coupled to electrostatic interactions between the carboxylate and the protonated amino group of the cyclodextrin.
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Affiliation(s)
- G Galaverna
- Dipartimento di Chimica Organica e Industriale, Università di Parma, Italy
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Abstract
This review presents the different chiral selectors used in capillary electrophoresis (CE) for the separation of enantiomers. The use of charged cyclodextrins, crown ethers, polysaccharides, proteins, natural and synthetic micelles, macrocyclic antibiotics and ergot alkaloids is discussed in detail. Neutral native and derivatized cyclodextrins are not treated because several review articles have already been published on this topic. Recent developments like the application of two chiral selectors in the same background electrolyte are highlighted.
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Affiliation(s)
- K Verleysen
- Department of Organic Chemistry, University of Gent, Belgium
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Schneider HJ, Hacket F, Rüdiger V, Ikeda H. NMR Studies of Cyclodextrins and Cyclodextrin Complexes. Chem Rev 1998; 98:1755-1786. [PMID: 11848948 DOI: 10.1021/cr970019t] [Citation(s) in RCA: 1142] [Impact Index Per Article: 43.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hans-Jörg Schneider
- Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226, Japan
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29
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Owens PK, Fell AF, Coleman MW, Berridge JC. Effect of charged and uncharged chiral additives on the resolution of amlodipine enantiomers in liquid chromatography and capillary electrophoresis. J Chromatogr A 1998. [DOI: 10.1016/s0021-9673(97)00995-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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