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  • 1
    Electronic Resource
    Electronic Resource
    Oxidation cyclischer Ether durch Iod-tris (trifluoracetat). Synthese und NMR-Analyse von trifluoracetylierten Desoxypentopyranosen und von 3-Desoxy-threo-pentose (1983)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 1950-1958 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Oxidation of Cyclic Ethers by Iodine Tris(trifluoroacetate). - Synthesis and NMR Analysis of Trifluoroacetylated Deoxypentopyranoses and of 3-Deoxy-threo-pentoseOxidation of tetrahydro-2H-pyran (2) by iodine tris(trifluoroacetate) (1) yields the dideoxypentopyranose derivates 3a-b and the ring-contracted compound 4. Similarly, 3-(trifluoroacetoxy)-tetrahydro-2H-pyran (5) is oxidized to yield the deoxypentopyranose derivatives 6a-d and the ring-contracted compound 7. Hydrolysis of 6b yields 3-deoxy-threo-pentose 8 which is thus available in 3 or 4 steps, respectively, instead of 9 steps before. The solution of 8 in water contains the 4 ring-tautomers 8a-d. - Analysis of the 1H NMR spectra of 6a-d reveals that (a) the anomeric effect of the trifluoroacetoxy group is larger than that of the acetoxy group and (b) that the 1H signals are shifted downfield by trifluoroacetoxy groups (OX) located in γ or even in δ position, provided that H and OX have a well-defined orientation.
    Notes: Iod-tris(trifluoracetat) (1) oxidiert Tetrahydro-2H-pyran (2) zu den Didesoxypentopyranosederivaten 3a-b und dem Ringverengungsprodukt 4. 3-(Trifluoracetoxy) tetrahydro-2H-pyran (5) ergibt analog die Desoxypentopyranosederivate 6a-d und das Ringverengungsprodukt 7. Hydrolyse von 6b führt zu 3-Desoxy-threo-pentose (8), die damit in 3 bzw. 4 Synthesestufen erhältlich ist, während bisher 9 Stufen erforderlich waren. 8 existiert in wäßriger Lösung als Gemisch der vier Ringtautomeren 8a-d. - Analyse der 1H-NMR-Spektren von 6a-d ergibt, daß(a) der anomere Effekt der Trifluoracetoxygruppe größer ist als der der Acetoxygruppe und (b) die 1H-Signale durch γ- und sogar durch δ-ständige Trifluoracetoxygruppen (OX) tieffeldverschoben werden, vorausgesetzt, H und OX weisen eine bestimmte Orientierung zueinander auf.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198319831110
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclodopa glucoside ( = (2S)-5-(β-D-glocopyranosyloxy)-6-hydroxyindoline-2-carboxylic acid) and its occurrence in red beet (beta vulgaris var. rubra L.) (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1348-1355 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclodopa glucoside ( = (2S)-5-(β-D-glucopyranosyloxy)-6-hydroxyindoline-2-carboxylicacid; 1a) is prepared from betainin (2a) via a base exchange reaction. Its purification and physical properties are described. The compound is N-formylated in dilute HCOOH solution. Cyclodopa glucoside is contained in considerable amount in redbeet juice varying from 0.07 to 1.9 mmol/kg or from 12 to 46% relative to teh content of betanin. Teh occurrence of free cyclodopa glucoside supports its role as intermediate in betanin biosynthesis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670520
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  • 3
    Electronic Resource
    Electronic Resource
    Bestimmung des Aggregationsgrads lithiumorganischer Verbindungen durch Kryoskopie in Tetrahydrofuran (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1972-1988 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Degree of Aggregation of Organolithium Compounds by Means of Cryoscopy in TetrahydrofuranThe association behaviour of alkyl-, aryl- and alkinyl-lithium compounds as well as of lithium enolates and chiral lithium azaenolates is determined from freezing-point depression values in dilute tetrahydrofuran solutions at -108°C. Compared toX-ray-crystallographic data (lithiated methyldithiane, phenyllithium, lithio derivatives of a ketone, carboxylic amide and -ester, and a diketopiperazine-bislactim-ether), desaggregation is found under these conditions. The structures determined by 13C-NMR spectroscopy for BuLi, lithiophenylacetylene and (t-butyl)lithioacetylene are confirmed. The dilithio salt of a carboxylic acid is polymeric, a chiral lithio-hydrazone and a chiral lithio-oxazolidine are monomeric and dimeric, respectively. Lithium diisopropylamide is a monomer-dimer equilibrium mixture. The apparatus described permits both synthesis and measurement of the reactive species under inert atmosphere conditions in the same vessel.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670736
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  • 4
    Electronic Resource
    Electronic Resource
    Gerüstumlagerung eines α,β -ungesättigten γ,δ-Epoxiketons bei der Birch-Reduktion: Strukturaufklärung mittels 13C-INADEQUATE-NMR-Spektroskopie (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 2231-2235 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Skeleton Rearrangement of an α-β-Unsaturated γ,δ-Epoxyketone during Birch Reduction: Structure Elucidation by Means of 13C-INADEQUATE-NMR SpectroscopyWhen the γ-epoxide 2 of β-ionone is treated under standard Birch-reduction conditions, unexpectedly a 70% combined yield of regioisomeric octalones 4 and 5 is isolated. These products unquestionably result form cleavage of the central epoxide C=C bond. The structure of compounds 4 and 5 could be determined by means of 13C-INADEQUATE-NMR spectroscopy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670827
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesen und Eigenschaften von Pyrrolindigo-VerbindungenHerrn Professor Dr. Hans Plieninger in Verehrung gewidmet. (1980)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 564-589 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses and Properties of Pyrrolindigo CompoundsHerrn Professor Dr. Hans Plieninger in Verehrung gewidmet.4,4′,5,5′,6,6′,7,7′-Octahydroindigo (9c), 4,4′-dibutyl-5,5′-dimethylpyrrolindigo (9a) and di(cyclopenta)pyrrolindigo (9d) as well as the condensation products from 2-pyrrolin-4-ones with benzal-dehyde, isatin, glyoxale, and 2-methoxy-3-indolone, plus N-methyl- and N,N′-dimethylderivatives of 9c and tetrahydroindigo 31 were all synthesized and compared with other indigoids especially the corresponding benzoannelated compounds. The unusual behavior of N-methylindigoids is discussed. In the boron chelate 39 of 1-methyl-4,5,6,7-tetrahydroindigo the structure of a fixed tautomeric indigo is approached.
    Notes: 4,4′,5,5′,6,6′,7,7′-Octahydroindigo (9c), 4,4′-Dibutyl-5,5′-dimethylpyrrolindigo (9a) und Di(cyclo penta)pyrrolindigo (9d) sowie die Kondensationsprodukte von 2-Pyrrolin-4-onen mit Benzaldehyd, Isatin, Glyoxal und 2-Methoxy-3-indolon, weiterhin N-Methyl- und N,N′-Dimethylderivate von 9c sowie Tetrahydroindigo 31 wurden synthetisiert und mit anderen Indigoiden, insbesondere den entsprechenden Benzo-anellierten Verbindungen, verglichen. Das ungewöhnliche Verhalten von N-Methylindigoiden wird diskutiert. Im Borchelat 39 von 1-Methyl-4,5,6,7-tetrahydroindigo ist die Struktur eines fixierten, tautomeren Indigos annähernd verwirklicht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198019800410
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetik, Katalyse und Mechanismus der Sekundärreaktion in der Schlußphase der Formose-Reaktion (1984)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 623-635 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Kinetics, Catalysis, and Mechanism of the Secondary Reaction in the Final Phase of the Formose ReactionIn the final phase of the formose reaction sugars are formed by the reaction of glycolaldehyde, glyceraldehyde and dihydroxyacetone. The application of high-pressure liquid chromatography allows for the first time to investigate intermediate and final products quantitatively. The results of kinetical investigations allow to suggest a reaction mechanism for the secondary reaction in the final phase of the formose reaction. This mechanism is compared with that of the starting phase and other known mechanisms. From the results metal ion-catalyzed aldol reactions have to be assumed.
    Notes: In der Schlußphase der Formose-Reaktion entstehen im Rahmen von Sekundärreaktionen (Selbst-und Mischadditionen von Glycolaldehyd, Glycerinaldehyd und Dihydroxyaceton) höhere Zucker. Aufgrund der Ergebnisse hochdruckflüssigkeitschromatographischer Untersuchungen können erstmalig quantitative Aussagen über die Zwischen- und Endprodukte von Einzelreaktionen gemacht werden: Aus den Ergebnissen kinetischer Untersuchungen und den Produktverteilungen wird ein Mechanismus für die Schlußphase der Sekundärreaktionen abgeleitet und dieser mit dem der Anfangsphase sowie mit anderen bekanntgewordenen Mechanismen verglichen. Es handelt sich um durch Metall-Ionen katalysierte Aldolreaktionen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198419840402
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