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  • Inorganic Chemistry  (3)
  • 1970-1974  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Anwendungen der 13C-Resonanz-Spektroskopie, XI. Pteridin-Spektren, I (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 3951-3961 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Applications of 13C Resonance Spectroscopy, XI. Pteridin Spectra, IThe 13C n.m.r. spectra of several pteridines, among others the biological important :compounds folic acid and amethopterine, have been measured and assigned in neutral and alkaline solution. The pH-dependence of the totale spectrum was recorded and a pKa-value of 9.2 has been determined.
    Notes: Die 13C-NMR-Spektren verschiedener Pteridine, u. a. die der biologisch wichtigen Verbindungen Folsäure und Amethopterin, wurden in neutraler und alkalischer Lösung vermessen und zugeordnet. Die pH-Abhängigkeit des Folatspektrums wurde verfolgt und ein pKa-Wert von 9.2 bestimmt.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731061218
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  • 2
    Electronic Resource
    Electronic Resource
    Anwendungen der 13C-Resonanz-Spektroskopie, XVIII. Pteridin-Spektren, III (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 3275-3286 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Applications of 13C Resonance Spectroscopy, XVIII. Pteridin Spectra, IIIThe 13C n.m.r. spectra of pterine (2-amino-4-oxo-3,4-dihydropteridine, 1), lumazine (2,4-dioxo-1,2,3,4-tetrahydropteridine, 2), 7-pterine carboxylic acid (3) and 4-oxo-3,4-dihydropteridine (4) have been measured in acidic solution (CF3CO2H, 2 N H2SO4, FSO3H) and assigned. The structure of the mono-and dications was derived from protonation shifts of the 13C resonances and changes in the 13C, 1H coupling constants. Contrary to earlier 1H n.m.r. based findings, the 13C data are only compatible with the second protonation occuring at N-5. The importance of the ΔE-term for the chemical shifts of 13C resonances is stressed.
    Notes: Die 13C-NMR-Spektren von Pterin (2-Amino-4-oxo-3,4- dihydropteridin, 1), Lumazin (2,4-Dioxo-1,2,3,4-tetrahydropteridin, 2), 7-Pterincarbonsäure (3) und 4-Oxo-3,4-dihydropteridin (4) wurden in saurer Lösung (CF3CO2H, 2 N H2SO4, FSO3H) gemessen und zugeordnet. Aus den Protonierungsverschiebungen der 13C-Resonanzen und den Änderungen der 13C, 1H-Kopplungskonstanten wurden die Strukturen der Mono- und Dikationen abgeleitet. Im Gegensatz zu früheren 1H-NMR-Befunden sind die 13C-Daten nur mit Zweitprotonierung an N-5 vereinbar. Die Bedeutung des ΔE-Terms für die chemische Verschiebung der 13C-Resonanz wird hervorgehoben.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741071015
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  • 3
    Electronic Resource
    Electronic Resource
    Anwendungen der 13C-Resonanz-Spektroskopie, XII. Pteridin-Spektren, II (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 876-886 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Applications of 13C Resonance Spectroscopy, XII. Pteridin Spectra, IIIt is shown that HMO π-charge densities of nitrogen heterocycles correlate nearly as good with 13C resonance frequencies as INDO total charge densities. For pteridin anions the relation Δδ = 193.1 Δπ(HMO) [S(E) = 8.1 ppm] is obtained using benzene as reference. With the help of this equation the assignment of the 13C resonances in the anions of 6,7-dioxo-5,6,7,8-tetrahydropteridin, 2,4,6,7 -tetroxo-1,2,3,4,5,6,7,8-octahydropteridin, leucopterin and alloxazine is derived.
    Notes: Es wird gezeigt, daß HMO-π-Ladungsdichten in Stickstoff-Heterocyclen mit den 13C -Resonanzfrequenzen nahezu ebenso gut korrelieren wie INDO-Gesamtladungsdichten. Für Pteridin-Anionen erhält man mit Benzol als Referenz die Beziehung Δδ = 193.1 Δπ(HMO) [S(E) = 8.1 ppm], mit deren Hilfe die Zuordnungen der 13C-Resonanzen in den anionen von 6,7-Dioxo-5,6,7,8-tetrahydropteridin, 2,4,6,7-Tetroxo-1,2,3,4,5,6,7,8-octahydropteridin, Leukopterin und Alloxazin abgeleitet werden.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741070314
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