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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1975 (1975), S. 660-671 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses with Cyclic Mono-or Dialkynes and Butadiene; Ring Expansion by 4, 8, and 16 C-AtomsCyclic mono- and dialkynes can be co-oligomerized with two or four molecules of butadiene to di- and tricyclic cis-1,cis-4,trans-7-cyclodecatriene derivatives. Cyclododecyne, 1,8-cyclotetradecadiyne, and 5-oxa-1,8-cyclotetradecadiyne have been subjected to such reaction. Partial hydrogenation of the ten-membered rings formed and their oxidative cleavage to di- and tetraketones lead to a ring enlargement by 8 or 16 carbon atoms. It is shown using as example the cyclodecatriene derivative formed from cyclododecyne and two molecules of butadiene, that the same reactions lead (after thermal rearrangement of the ten-membered rings to the correspondending cis-4,5-divinylcyclohexenes) to a ring enlargement by 4 C-atoms and simultaneous introduction of two ethyl groups.
    Notes: An Nickel-Ligand-Katalysatoren lassen sich cyclische Mono- und Dialkine mit zwei oder vier Molekülen Butadien zu di- bzw. tricyclischen cis-1, cis-4, trans-7-Cyclodecatrienderivaten verknüpfen. Als Alkine wurden Cyclododecin, 1,8-Cyclotetradecadiin und 5-Oxa-1,8-cyclotetradecadiin eingesetzt. Partielle Hydrierung der gebildeten Zehnringe und deren oxidative Spaltung zu Di- oder Tetraketonen führt zu einer Ringerweiterung um 8 bzw. 16 C-Atome. Am Beispiel des Cyclodecatrienderivates aus Cyclododecin und zwei Molekülen Butadien wird gezeigt, daß die gleichen Reaktionen nach thermischer Umlagerung der Zehnringe in die entsprechenden cis-4,5-Divinylcyclohexene zu einer Ringerweiterung um 4 C-Atome und gleichzeitiger Einführung einer Diäthylgruppierung führen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 6 (1992), S. 463-478 
    ISSN: 0268-2605
    Keywords: Hydrotreatment ; hydrodesulfurization ; hydrodenitrogenation ; molybdenum ; clusters ; thiophene ; pyridine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sulfide cluster-derived ensembles are promising models of the active sites in commercial hydrotreatment catalysts. A series of sulfide clusters were adsorbed intact onto high-surface-area γ-alumina, magnesium oxide and activated carbon supports, then pretreated to produce highly dispersed catalytic ensembles with sizes similar to those of their precursor clusters. The activities of the bimetallic cluster-derived catalysts were significantly higher than those of the monometallic catalysts. We took this as evidence that direct interactions between molybdenum and the promoter element cause the promotional effect observed in commercial hydrotreatment catalysts. The hydrodesulfurization and hydrodenitrogenation activities correlated with the extent of molybdenum reduction. Our results suggested that the active sites in promoted hydrotreatment catalysts are centered on molecular-scale ensembles containing molybdenum, sulfur and the promoter element.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-01-21
    Description: Quality control mechanisms prevent the cell surface expression of incompletely assembled multisubunit receptors such as the T cell receptor (TCR). The molecular chaperone function of calnexin (IP90, p88), a 90-kilodalton protein that resides in the endoplasmic reticulum (ER), in the retention of representative chains of the TCR-CD3 complex in the ER was tested. Truncation mutants of calnexin, when transiently expressed in COS cells, were exported from the ER and either accumulated in the Golgi or progressed to the cell surface. CD3 epsilon chains cotransfected with the forms of calnexin that were not retained in the ER exited the ER and colocalized with calnexin. Since engineered calnexin determined the intracellular localization of the proteins associated with it, it is concluded that calnexin interacts with incompletely assembled TCR components and retains them in the ER.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rajagopalan, S -- Xu, Y -- Brenner, M B -- New York, N.Y. -- Science. 1994 Jan 21;263(5145):387-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Rheumatology and Immunology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8278814" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antigens, CD3/*metabolism ; Base Sequence ; Calcium-Binding Proteins/analysis/chemistry/*metabolism ; Calnexin ; Cell Line ; Cell Membrane/metabolism ; Endoplasmic Reticulum/*metabolism ; Golgi Apparatus/metabolism ; Histocompatibility Antigens Class I/metabolism ; Lysosomes/metabolism ; Membrane Proteins/analysis/chemistry/*metabolism ; Molecular Sequence Data ; Nuclear Envelope/metabolism ; Receptor-CD3 Complex, Antigen, T-Cell/*metabolism ; Recombinant Proteins/metabolism ; Transfection
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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