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  • 1
    Electronic Resource
    Electronic Resource
    Asymmetric sorbents based on mono- and diamines and resolution of racemates by ligand-exchange chromatographyPart 10 of “Ligand-Exchange Chromatography of Racemates”. Part 9: cf.8. (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2101-2107 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The asymmetric sorbents A, B, C, and D were prepared by interaction of a chloromethylated styrene copolymer of the isoporous macronet type (5,5% of crosslinks) with the chiral amines (S)-1-phenylethylamine, (R)-1,2-propanediamine, and their derivatives. Resins A and B, based on 1-phenylethylamine, do not sorb Cu(II) ions, whereas resins C and D, based on 1,2-propanediamine saturated with Cu(II) ions, were successfully used for ligand-exchange chromatography of amino acids, showing higher affinity to aminodicarboxylic acids than to diaminocarboxylic acids. Sorbent D displays an enantioselectivity of α ≥ 1,5 towards amino acids like Ala, Abu, Ser, or Lys and provides quantitative resolution of enantiomers of some other amino acids. L-amino acids are retained longer by resins C and D than D-isomers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021800905
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  • 2
    Electronic Resource
    Electronic Resource
    Highly crosslinked chitosan gels (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1863-1869 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chitosan was crosslinked to varying extents with bis(vinylsulfonyl)arenes as crosslinking agents in homogeneous solution. The effect of reaction conditions on the onset of gelation was investigated. The rate of gelation was shown to depend on the chitosan concentration and the structure of the crosslinking agent used. The degree of crosslinking and content of the remaining pendant double were evaluated. The obtained cnitosan gels swell both in organic solvents and in acidic aqueous solutions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940701
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  • 3
    Electronic Resource
    Electronic Resource
    Ligand-exchange chromatography of racemates, 9.Part 8: cf.15 Ligand-exchange chromatography of amino acid enantiomers on asymmetric sorbents with polydentate sulfur containing groupings (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2121-2132 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The paper describes the syntheses of four asymmetric sorbents, which contain S-(2-aminoethyl)-L-cysteine (1a), S-(carboxymethyl)-L-cysteine (1c), S,S′-(ethylene)-bis(L-cysteine) (2a), and N,N′-(ethylene)-bis(D-methionine) (3a) groupings as the chiral fixed ligands in a cross-linked polystyrene matrix. The sorbents were used for ligand-exchange chromatography of amino acid enantiomers in the presence of Cu(II) and Ni(II) ions. Enantioselective effects in the formation of mixed-ligand complexes consisting of a fixed ligand, a metal ion, and an amino acid enantiomer were determined. The highest values of enantioselectivity reaching 1 300 to 1 890J/mol were found in mixed-ligand complexes containing histidine or β-phenyl-α-alanine.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021790901
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  • 4
    Electronic Resource
    Electronic Resource
    Enantioselective hydrolysis of α-amino acid esters catalysed by polymeric copper and nickel complexes (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 799-802 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021800323
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  • 5
    Electronic Resource
    Electronic Resource
    A vivid model illustrating chiral recognition induced by achiral structures (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 208-210 
    Details
    ISSN: 0899-0042
    Keywords: enantioselectivity ; three-point model ; didactic model ; chiral separations ; ligand-exchange chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If diastereomeric complexes are adsorbed on a surface or if they include a molecule of solvent, two points of attractive interaction between the chiral species of the complex can be sufficient for mutual chiral recognition of these species. In special cases even one single point of interaction is sufficient. This extension of the three-point contact rule of Dalgliesh, first observed in chiral ligand-exchange chromatogrphy, can be demonstrated by using hands.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530020403
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  • 6
    Electronic Resource
    Electronic Resource
    Letter to the editors: Should the terminology used in chirality be more precise? (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 442-442 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030605
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  • 7
    Electronic Resource
    Electronic Resource
    The nature of chiral recognition: Is it a three-point interaction? (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 99-102 
    Details
    ISSN: 0899-0042
    Keywords: chiral recognition ; enantioselectivity ; enantiospecificity ; three-point interaction rule ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evolution of the initial “three-point attachment model” resulted in the understanding that an interaction in at least three configuration-dependent points is needed for a chiral selector to recognize entantiomers. Thermodynamic enantioselectivity of this interaction can result in chiral discrimination of the enantiomers, with the exception of a temperature range where enthalpic and entropic contributions to the free energy of discrimination balance each other. Similarly, a three-point interaction is needed for a chiral inductor to modify enantiospecifically a prochiral molecule. The difference between a theoretical interaction point and real interaction sites in chemical molecules is emphasized. The role of conformational rigidity of chiral species is discussed in relation to the dependence of spatial arrangement of three active points on the configuration of the species. Chirality 9:99-102, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chiral discrimination phenomena in mixed-ligand copper(II) complexes with amino acids and 1,3-dicarbonyl compounds (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 303-309 
    Details
    ISSN: 0899-0042
    Keywords: enantioselectivity ; mixed-ligand copper complexes ; formation constants ; amino acids ; 1,3-dicarbonyl compounds ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism (CD) spectra of individual mixed-ligand copper(II) complexes of 1,3-dicarbonyl compounds, (1S)- or (1R)-3-hydroxymethylene camphor, (1S)-3-trifluoroacetyl camphor, or (1R)-2-hydroxymethylene menthone, and α-amino acids, alanine, valine, proline, or their N-alkyl derivatives, were calculated from CD spectra of equilibrium solutions containing the above constituents in methanol or ethylene dichloride. Diastereomeric mixed-ligand complexes incorporating identical dicarbonyl but enantiomeric N-alkyl-α-amino acid ligands exhibit quasi-enantiomeric CD spectra. Unsubstituted amino acids, on the contrary, will make no decisive contributions to the net optical activity spectrum of the mixed-ligand complexes. Formation constants of diastereomeric mixed-ligand complexes have been calculated from data on disproportionation of the latter into corresponding equally paired complexes. Enantioselectivity was demonstrated to amount to up to 700 cal/mol. Possible steric structures of mixed-ligand complexes are discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050505
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  • 9
    Electronic Resource
    Electronic Resource
    NMR investigations of the enantiomeric excess effects in solutions with weak intermolecular association (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 326-330 
    Details
    ISSN: 0899-0042
    Keywords: enantioselectivity ; NMR ; self-association ; achiral solvents ; dimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main features of statistically controlled associate diasteromerism (SCAD) in solution as measured by nuclear magnetic resonance (NMR) are discussed. In an achiral solvent, (R)- and (S)-enantiomers can demonstrate distinct NMR signals, with the intensity ratio equal to the concentration ratio. The previous theory of SCADA (anisochronism of nuclear magnetic moments caused by SCAD) is supplemented by treatment of enantiomeric excess phenomena in relation with the hypothesis that a sample consists totally of short-living diastereomeric dimers which are involved in fast (on the NMR time scale) exchange by enantiomers. Thermodynamic parameters of SCAD as well as limits for enantioselectivity phenomena are estimated. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070503
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of Isomeric N-Benzyl Derivatives of 1,2-Propanediamine (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 786-790 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese isomerer N-Benzylderivate des 1,2-PropandiaminsBenzaldehyd reagiert mit der 1-Aminogruppe des 1,2-Propandiamins viel leichter zur Schiffschen Base als mit der 2-Aminofunktion. Dieser Unterschied ermöglicht die Synthese aller isomeren Mono-sowie Dibenzylderivate von racemischem und chiralem 1,2-Propandiamin (Schema 1, Tabelle 1).
    Notes: Benzaldehyde reacts with the 1-amino group of 1,2-propanediamine (1) to give a Schiff base much more readily than with the 2-amino group. This difference permits synthesis of all the isomeric mono- and dibenzyl derivatives of racemic and chiral 1,2-propanediamine (Table 1, Scheme 1).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800518
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