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  • 1
    Electronic Resource
    Electronic Resource
    Reactivity of pyrrole pigments, part 13: Identification of the reaction product generated from bile pigments by the superoxide anion (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 653-663 
    Details
    ISSN: 1434-4475
    Keywords: Bilirubin metabolism ; pK a of biliverdins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden die UV/Vis-Spektren der konjugierten Basen (NH-Deprotonierung) von Biliverdin IX α (BV), Mesobiliverdin IX α (MBV), Biliverdin-IX α-dimethylester (BV - DME) und Mesobiliverdin-IX α-dimethylester (MBV - DME) bestimmt. Sie ähneln denen der Reaktionsprodukte, die man bei der Umsetzung dieser Biliverdinverbindungen mit Superoxydanion ( $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ ) erhält. Damit wird bewiesen, daß die Reaktion über eine N-Deprotonierung der Lactamgruppe verläuft, an die sich eine $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ -Dismutation anschließt. Die spektrometrische Titration vonBV, MBV und ihrer Dimethylester zeigt, daß der Lactamstickstoff in den vinylsubstituierten Biliverdinderivaten eine höhere Azidität aufweist (ΔpK a ℞0.5). Die Spektren der bis-deprotonierten konjugierten Basen der Bilatriene-abc (BV 4− undMBV 4−) wurden inDMSO/H2O/OH−-Systemen (H−℞23) erhalten. Unter Berücksichtigung der geringen Redoxpotentiale vonBV 3− und des entsprechenden Trianions von Bilirubin IX α (voltammetrische Bestimmung) wird ein neuer metabolischer Abbau für Bilirubin IX α vorgeschlagen: primäre Deprotonierung in lipophilem Medium mit $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ und nachfolgender Oxydation.
    Notes: Summary The UV/Vis spectra of the conjugated bases (NH deprotonation) of biliverdin IX α (BV), mesobiliverdin IX α (MBV), biliverdin IX α dimethyl ester (BV -DME) and mesobiliverdin IX α dimethyl ester (MBV - DME) are shown. They resemble those obtained for the reaction products of these biliverdins with superoxide anion ( $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ ). These results confirm that the bile pigments react with $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ giving the lactam NH deprotonated conjugated bases and inducing $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ dismutation. The spectrometric titrations ofBV, MBV and their dimehyl esters show that the lactam NH of the vinyl substituted biliverdins is more acidic (ΔpK a ℞0.5). The spectra of the lactam NH bisdeprotonated conjugated bases of the bilatrienes-abc studied (BV 4− andMBV 4−) can be obtained inDMSO/H2O/OH− systems of high basicity function (H−℞23). Because of the low oxidation potentials ofBV 3− and of the corresponding trianion of bilirubin IX α (studied by voltammetry) an alternative metabolic degradative pathway is suggested for bilirubin, involving the interaction in lipophilic media with $$o_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } $$ and oxidation of the conjugated base generated by NH deprotonation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809769
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  • 2
    Electronic Resource
    Electronic Resource
    On 3,5,6-trihalo-2-(pyrrol-2-yl)-1,4-benzoquinones (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 509-514 
    Details
    ISSN: 0947-3440
    Keywords: Pyrroles ; Polypyrrol ; p-Chloranil ; p-Bromanil ; p-Fluoranil ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the reaction of pyrroles with tetrahalo-1,4-benzoquinones two different processes occur: the oxidation of pyrrole and the coupling reaction to 3,5,6-trihalo-2-(pyrrol-2-yl)-1,4-benzoquinones. Excess of pyrrole results in doped polypyrrole as the principal reaction product. Excess of tetrahalobenzoquinone and dilution, provides the title compounds. The UV/Vis spectra and the electrochemical behaviour show that the title compounds have the HOMO localized at the pyrrole and the LUMO at the quinone ring.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950370
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  • 3
    Electronic Resource
    Electronic Resource
    Reactivity of pyrrole pigments, III. Fragmentation of nitro derivatives of pyrrole pigments and its relationship to the Gmelin reaction (1983)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 1-7 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktivität von Pyrrolpigmenten, III- Fragmentierung von Nitroderivaten von Pyrrolpigmenten und ihr Zusammenhang mit der Gmelin-ReaktionEs wird gezeigt, daß sich die 5-(Arylnitromethylen)-3-pyrrolin-2-one 1-5, die 5-Nitrobilin-1,19-dione 7, 8 und das 5 Nitropyrromethenon 6 in saurem Medium _ analog der Fragmentierung von Nitronsäuren _ zu Maleinimiden zersetzen. Durch diese Fragmentierung läßt sich die Gmelin-Reaktion und die Bildung des ‘Nitritkörpers’ (Methylvinylmaleinimid) erklären, der bei der Behandlung von Bilirubin mit salpetriger Säure auftritt.
    Notes: The 5-(arylnitromethylene)-3-pyrrolin-2-ones 1-5, the 5-nitrobilin-1,19-diones 7,8, and the 5-nitropyrromethenone 6 are shown to decompose in acidic media to yield maleimides according to fragmentation reactions of nitronic acids. This fragmentation reaction elucidates the nature of the Gmelin reaction and the formation of the “Nitritkörper” (methylvinylmaleimide) by nitrous acid treatment of bilirubin.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198319830102
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  • 4
    Electronic Resource
    Electronic Resource
    Reactivity of Pyrrole Pigments, VIII. Preparation of 5(2H)-Dipyrrylmethanones from 5(1H)-Pyrromethenones by Reduction with Sodium Dithionite (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1241-1247 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktivität von Pyrrolpigmenten, VIII(1). - Darstellung von 5(2H)-Dipyrrylmethanonen aus 5(1H)-Pyrromethenonen durch Reduktion mit Natriumdithionit5(1H)-Pyrromethenone 3 können mit Na2S2O4 in sehr guten Ausbeuten zu 5(2H)-Dipyrrylmethanonen 4 reduziert werden. Einige Reaktionsbedingungen wurden optimiert.
    Notes: 5(1H)-Pyrromethenones 3 have been reduced with sodium dithionite to give 5(2H)-dipyrrylmethanones 4 in very good yields. Some of the conditions to optimize this reduction have been studied.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860709
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  • 5
    Electronic Resource
    Electronic Resource
    Über die Anwendung von Lanthaniden-Verschiebungs-Reagenzien (LSR) bei der Strukturbestimmung flexibler Moleküle, am Beispiel des 2-Methyltetrahydropyrans und des cis-4-Methyl-2-(2′-methyl-1′-propenyl)- tetrahydropyransDiese Arbeit wurde subventioniert von der ‘Comision Asesora de Investigacion Cientifica y Tecnica de la Presidencia de Gobierno’. (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 467-472 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The model of Davis and Willcott can be successfully applied to 1H NMR lanthanide induced shifts (LIS) of 2-methyltetrahydropyran in the presence of Eu(dpm)3. By contrast, the model does not work in the case of cis-4-methyl-2-(2′-methyl-1′-propenyl)tetrahydropyran (cis-Rosenoxide), probably due to the presence of more than one LSR-substrate complex in the solution.
    Notes: Das Modell von Davis und Willcott lässt sich erfolgreich auf die LIS-Werte von 2-Methyltetrahydropyran mit Eu(dpm)3 anwenden. Im Fall des cis-4-Methyl-2-(2′-methyl-1′-propenyl)tetrahydropyrans (cis-Rosenoxyd) hingegen versagt es, wahrscheinlich weil in Lösung mehr als ein Komplex LSR-Substrat vorliegt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120806
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  • 6
    Electronic Resource
    Electronic Resource
    Significance testing of lanthanide shift reagent data (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 293-296 
    Details
    ISSN: 0749-1581
    Keywords: Significance testing ; LSR data ; Weighted agreement factors ; Hamilton R-ratio test ; jacknife test ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of weighted agreement factors in the significance testing of lanthanide-induced shift analysis is physically meaningless, and can manipulate the resulting significance values, as confirmed by the results found with two compounds. The Hamilton R factor ratio significance test and the jacknife test are compared for these compounds. The R ratio test is more easily applied; the jacknife test does not show any clear advantage and is more sensitive to changes originating from the use of weighted agreement factors.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250403
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