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  • 1
    Electronic Resource
    Electronic Resource
    Singlet Oxygen Quenching Abilities of CarotenoidsDedicated to Professor Waldemar Adam on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1887-1893 
    Details
    ISSN: 0947-3440
    Keywords: Carotenoids ; Isonorastacene synthesis ; Singlet oxygen ; Effective chain length ; Second-order quenching rate constants ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bimolecular rate constants kq for quenching of singlet oxygen (1Δg state) by 26 different natural and novel synthetic carotenoids were determined at 37 °C in a mixture of chloroform and ethanol. The steady-state technique used involves the generation of 1O2 by thermal decomposition of disodium 3,3′-naphtalene-1,4-diyl-dipropionate endoperoxide (NDPO2) and the detection of its luminescence intensity at 1270 nm. Excitation energies (π,π*, 11Ag → 11Bu) and absorption maxima (430-590 nm) vary in the broadest range. Deeply coloured blue carotenoids are also included in the studies for the first time. An empirical correlation between the π,π* (11Ag → 11Bu) excitation energy and carotenoid structure (effective chain length Neff) was found: E(S) = 12642 cm-1 + 92027 cm-1 × 1/Neff. The quenching ability of the investigated carotenoids depends on the excitation energy of their transition at long wavelengths in a characteristic way showing as limiting factors either the thermal Arrhenius activation or the diffusion-controlled rate. This dependence and the suspected relationship between singlet E(S) and triplet E(T) energies, respectively, are discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970913
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  • 2
    Electronic Resource
    Electronic Resource
    Convenient Synthesis of Biologically Important Retinoids (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 717-720 
    Details
    ISSN: 0947-3440
    Keywords: Vitamin A derivatives ; Retinoic acid derivatives ; Tumor inhibitors ; Koenigs-Knorr reaction ; Glucuronides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The toxic and teratogenic effects caused by the highly biologically active (all-E)-retinoic acid and its derivatives prompted us to synthesize a number of retinoids. We developed synthetic approaches to (all-E)-retinyl β-D-glucuronide 3, methyl (retinoyl β-D-glucopyranoside)uronate 5, (all-E)-retinoic acid β-D-glucopyranosyl ester 8 and (all-E)-retinoyl β-D-glucuronide 6 in high purity and yield. Compound 3 was synthesized under Koenigs-Knorr conditions from (all-E)-retinol and an α-halogenose. Compounds 5 and 8 were prepared by esterification of a silver salt of (all-E)-retinoic acid with an α-glycosyl halide in pyridine. (all-E)-Retinoyl β-D-glucuronide 6 was prepared by reaction of (all-E)-retinoyl fluoride with underivatized β-D-glucuronic acid. Compounds 5, 6 and 8 show biological effects similiar to those of retinoic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199504106
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  • 3
    Electronic Resource
    Electronic Resource
    Oxidation von Phosphor-Yliden mit Hydroperoxiden: Ein neuer und ergiebiger Weg zu symmetrischen CarotinoidenHerrn Prof. Dr. H. H. Inhoffen Zum 70. Geburtstag gewidmet. (1977)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1977 (1977), S. 1146-1159 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hydroperoxide Oxidation of Phosphorous Ylides: A New and Useful Route to Symmetrical CarotenoidsResonance stabilized alkylidenetriphenylphosphoranes are oxidized to symmetrical olefins and triphenylphosphine oxide using hydrogen peroxides. A preferred procedure consists in reacting aqueous solutions of the phosphonium salts with hydrogen peroxide in the presence of weak bases. Using this approach, β-carotene and other symmetrical carotenoids can be prepared conveniently and in good yields.
    Notes: Resonanzstabilisierte Alkylidentriphenylphosphorane werden durch Hydroperoxide zu symmetrischen Olefinen und Triphenylphosphinoxid oxidiert. Eine bevorzugte Arbeitsweise ist die Umsetzung wäßriger Lösungen der betreffenden Phosphoniumsalze mit Perhydrol in Gegenwart schwacher Basen. β-Carotin und andere symmetrische Carotinoide lassen sich auf diesem Wege bequem und in guten Ausbeuten herstellen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197719770711
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  • 4
    Electronic Resource
    Electronic Resource
    Racematspaltung von Pantolacton mit neuen chiralen AminenHerrn Prof. Dr. G. Wittig zum 80. Geburtstag gewidmet. (1978)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 1024-1029 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Resolution of Pantolactone Using New Chiral AminesThe diastereomeric salts 9/10 and 11/12, formed from (RS)-pantoic acid and the new optically active amines 5 and 8, can be easily separated. Using ( + )-5 as resolving agent, ( - )-(R)-pantolactone (R-1) is obtained in 90% yield and 94% optical purity.
    Notes: Die neuen, optisch aktiven Amine 5 und 8 bilden mit (RS)-Pantoinsäure die leicht trennbaren, diastereomeren Salze 9/10 und 11/12. Mit ( + )-5 als Spaltungsreagenz läßt sich ( - )-(R)-Pantolacton (R-1) in einer Ausbeute von 90% und einer optischen Reinheit von 94% gewinnen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197819780612
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  • 5
    Electronic Resource
    Electronic Resource
    ( + )-Biotin aus D-ArabinoseHerrn Prof. Dr. Matthias Seefelder zum 60. Geburtstag gewidmet. (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 1972-1977 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: ( + )-Biotin from D-ArabinoseStarting from D-arabinose, Wittig-reaction of the partially protected derivative 8 afforded the intermediate 17 which can be transformed into ( + )-biotin (1).
    Notes: Aus D-Arabinose wird über eine Wittig-Reaktion des teilgeschützten Derivates 8 das Zwischen-produkt 17 gewonnen, das in ( + )-Biotin (1) übergeführt werden kann.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019801207
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