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  • Chemistry  (99)
  • Enantioselective gas chromatography  (9)
  • Inorganic Chemistry  (6)
  • Cyclodextrins  (2)
  • Dynamic gas chromatography  (2)
  • 11
    Digitale Medien
    Digitale Medien
    Unusual retention behavior of methyl lactate and methyl 2-hydroxybutyrate enantiomers on a modified cyclodextrin (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 694-695 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; Reversal of elution order ; Isoenantioselective temperature ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240141013
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  • 12
    Digitale Medien
    Digitale Medien
    Diluted versus undiluted cyclodextrin derivates in capillary gas chromatography and the effect of linear carrier gas velocity, column temperature, and length on enantiomer separation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 5 (1993), S. 35-40 
    Details
    ISSN: 1040-7685
    Schlagwort(e): Enantiomers ; gas chromatography ; cyclodextrin derivatives ; temperature dependence ; capillary columns ; selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of dilution of the chiral stationary phase octakis (3-O-butyryl-2, 6-di-O-pentyl)-γ-cyclodextrin in the achiral polysiloxane OV-1701 on the separation factor was investigated over a wide concentration range. The loss in enantioselectivity was only negligible down to a dilution of 50% (w/w), since the separation factor vs. concentration curves levels off at higher concentrations. Because of the strong temperature dependence of the separation factors, the properties of short columns (10 m and 4.5 m) were evaluated. These short columns, which allow operation at low temperatures and lead to enhanced separation factors were found to be appropriate for the separations of simple mixtures, because the gain in selectivity exceeded the loss in separation efficiency. For complex mixtures, the higher efficiencies of columns of at least 25 m in length were still necessary. A plot of In α vs. 1/T did not yield straight lines, but showed a significant curvature, leading to considerable relative errors if thermodynamic data were derived from these plots.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mcs.1220050105
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  • 13
    Digitale Medien
    Digitale Medien
    Separation of basic drugs by capillary electrophoresis using selectively modified cyclodextrins as chiral selectors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 355-363 
    Details
    ISSN: 1040-7685
    Schlagwort(e): basic drugs ; capillary electrophoresis ; cyclodextrin derivatives ; separation of enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence of seven differently methylated β-cyclodextrin derivatives and of pure β-cyclodextrin (β-CD) on the enantiomeric resolution by capillary electrophoresis of six basic chiral pharmaceuticals is investigated. The methyl substitution pattern affects enantioselectivity much more than other experimental parameters. The purity of the used cyclodextrin derivatives is analyzed by successive hydrolysis, reduction, acetylation, and GC/MS of each CD derivative and by MALDI-TOF mass spectrometry. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mcs.1220070408
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  • 14
    Digitale Medien
    Digitale Medien
    Stereochemical analysis of constituents of essential oils and flavor compounds by enantioselective capillary gas chromatography (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 328-332 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; Cyclodextrin derivatives ; Terpenoid hydrocarbons ; Chiral carbonyl compounds ; Flavor alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Modified cyclodextrins interact enantioselectively with a great variety of volatile chiral constituents of essential oils by forming diastereomeric inclusion complexes. Capillary gas chromatography is used for resolving the enantiomers of terpenoid hydrocarbons (camphene, α-pinene, limonene, α-phellandrene), carbonyl compounds (carvone, fenchone, menthone, isomenthone, piperitone, camphor, myrtenal), and alcohols (trifluoroacetylated β-citronellol, myrtenol, trans-pinocarveol, 1-octen-3-ol, and underivatized linalool). The enantiomeric composition of some of these compounds in a variety of essential oils is investigated.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240130507
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  • 15
    Digitale Medien
    Digitale Medien
    Gas chromatographic separation of atropisomeric alkylated and polychlorinated biphenyls using modified cyclodextrins (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 376-378 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Resolution of atropisomers ; Alkylated biphenyls ; Polychlorinated biphenyls (PCBs) ; Dynamic gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Selectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′-dimethyl and 2,2′-diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2-Isopropyl-2′-t-butyl- and 2,2′-di-t-butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′-diisopropyl- and 2,2′-bis(trifluoromethyl)biphenyl show temperature-dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240160609
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  • 16
    Digitale Medien
    Digitale Medien
    Enantiomeric composition of the chiral constituents in essential oils. Part 1: Monoterpene hydrocarbons (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 184-189 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; Cyclodextrin derivatives ; Monoterpene hydrocarbons ; Essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Using a dual column gas chromatograph equipped with two capillary columns coated with heptakis(6-O-methyl-2,3-di-O-pentyl)-β-cyclodextrin (6-me-2,3-pe-β-CD) and octakis(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin (6-me-2,3-pe-γ-CD), respectively, all important olefinic monoterpene hydrocarbons occurring in essential oils, including α-thujene, α- and β-pinene, camphene, sabinene, α- and β-phellandrene, Δ-3-carene and limonene can be resolved into enantiomers. With the chromatographic system described the characteristic enantiomeric composition of these monoterpene hydrocarbons in essential oils can be determined.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240150310
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  • 17
    Digitale Medien
    Digitale Medien
    New, selectively substituted cyclodextrins as stationary phases for the analysis of chiral constituents of essential oils (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 367-372 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; Two-dimensional GC ; Essential oils ; Lavandulol ; α-Bisabolol ; Nerolidol ; Methyl jasmonate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New β- and γ-cyclodextrin derivatives, selectively substituted with n-pentyl and methyl groups, e.g. heptakis(2,6-di-O-methyl-3-O-pentyl)-β-cyclodextrin, octakis(2-O-methyl-3,6-di-O-pentyl)-γ-cyclodextrin, and octakis(2,6-di-O-methyl-3-O-pentyl)-γ-cyclodextrin, have been prepared from specifically protected intermediates. The new cyclodextrin derivatives exhibit unique enantioselectivity towards important chiral constituents of essential oils. The enantiomers of lavandulol, α-bisabolol, nerolidol, and other terpenoid alcohols could be resolved and their presence in different essential oils could be proved. Methyl jasmonate and epi-methyl jasmonate could, in addition, be detected in jasmine concrete by two-dimensional gas chromatography. The enantiomers of the macrocyclic ketone muscone have been separated for the first time.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240150603
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  • 18
    Digitale Medien
    Digitale Medien
    Gas chromatographic enantiomer separation with modified cyclodextrins: Carboxylic acid esters and epoxides (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 175-181 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; 2,6-di-O-methyl-3-O-pentyl-β- and y-cyclodextrins ; α and β hydroxy acids ; Branched carboxylic acids ; Non-steroidal anti-inflammatory drugs ; Abscisic Acid ; Epoxides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The wide range of application of 2,6-di-O-methyl-3-O-pentyl-β-and y-cyclodextrins is demonstrated by the resolution of the enantiomers of the methyl esters of chiral carboxylic acids: α and β hydroxy acids with up to 18 carbon atoms, hydroxy di- and tricarboxylic acids, and alkyl/aryl-substituted carboxylic acid methyl esters, including the plant hormone abscisic acid, insect juvenile hormones, and some non-steroidal anti-inflammatory drugs can be resolved with generally large separation factors. The new cyclodextrin derivatives also exhibit high selectivity for epoxides.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240160309
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  • 19
    Digitale Medien
    Digitale Medien
    Enantiomeric composition of the chiral constituents of essential oils. Part 2: Sesquiterpene hydrocarbons (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 315-320 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective GC ; Sesquiterpene hydrocarbons ; Cyclodextrin derivatives ; Essential oils ; Liverworts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A number of sesquiterpene hydrocarbons commonly occurring in essential oils has been prepared as racemic mixtures by chemical synthesis. Preparative gas chromatography with selectively per-O-alkylated cyclodextrins has been employed for the isolation of enantiomeric mixtures or pure enantiomers from the essential oils of higher plants and liverworts (Hepaticae). The enantiomers of α-curcumene, α- and β-bisabolene, β-elemene, δ-elemene, α-copaene, δ-cadinene, cis- and trans-calamenene, and bicyclogermacrene could be resolved by enantioselective gas chromatography on capillary columns coated with cyclodextrin derivatives. The enantiomeric composition of these sesquiterpene hydrocarbons in various essential oils was determined.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240170507
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  • 20
    Digitale Medien
    Digitale Medien
    Novel Chiral Pyridine N-Oxide Ligands and Their Application in the Enantioselective Catalytic Reduction of Ketones and the Addition of Diethylzinc to Aldehydes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1001-1007 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Pyridine N-oxide ; Pyridine ; Asymmetric catalysis ; Amino acids ; Amino alcohols ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Starting from picolinic acids 3 and 4, the amino acid-derived 2-aminoacylpyridine N-oxides 1a,c-e and 2,6-bis(aminoacyl)pyridine N-oxides 2b-e can be prepared in two steps by the coupling of picolinic acid N-oxides 5 and 6 under Appel conditions with the corresponding L-amino acid ester or (1R,2S)-norephedrine. Compounds 1 and 2 were used as chiral ligands in two different asymmetric catalyses. In the catalytic addition of diethylzinc to benzaldehyde 11, low enantioselectivities (2-29% ee) were obtained regardless of the amino acid moiety. However, the corresponding 2,6-bis(aminoacyl)pyridines 7 and 8 led to increased ee values (55% ee). In the catalytic reduction of ketones 9a-c to alcohols 10a-c low enantioselectivities were observed for alanine-, valine-, and leucine-derived N-oxides 1a,c and 2b,c. An increase of selectivity was observed for bis-methionine ligand 2d (32-38% ee) relative to that of mono-methionine ligand 1d (7-16% ee). However, mono-norephedrine ligand 1e (≤ 64% ee) and the corresponding bis-norephedrine ligand 2e (≤ 51% ee) displayed the highest selectivities. The influence of the N-oxide moiety on the enantioselectivity was demonstrated by the observation that 2,6-bis(aminoacyl)pyridines 7 and 8 gave much lower selectivities than the corresponding pyridine N-oxides 2d and e.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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