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  • 1
    ISSN: 0947-3440
    Keywords: Cage compounds ; Calculations ; Total syntheses ; Pyramidalization, olefinic ; Reactivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homo- and bishomododecahedral cage molecules with one and two O—CO (O—CH2) linkers installed into the parent pentagonal framework and featuring diverse functionalization patterns have been made available from pagodane precursors via highly expeditious synthetic sequences. The enforced geometrical changes with respect to molecular curvature, olefinic pyramidalization, transannular π,π-distance as well as to the chemical reactivity particularly of the unsaturated homododecahedranes are generally in good agreement with expectations based on calculations (MM2). In the appreciably pyramidalized monohomododecahedradiene skeleton 40 the non-parallel π-bonds are ca. 2.9 (3.1) Å [Φ = ca. 20 (32)°, MM2], in the bishomododecahedradiene skeleton 55 the perfectly syn-periplanar π-bonds 2.81 Å apart (Φ = 18.2°, X-ray crystal structure).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of 1,4-Pentadien-3-ones, 22. - Synthesis and Structure of the Epimers of 3,5-Diaryl-4-hydroxy-1,4-thiazinane 1,1-DioxidesDistyrylsulfones 1 react with the ambident nucleophile hydroxylamine only by double addition of nitrogen to give 4-hydroxy-1,4-thiazinane derivatives 3. In solution 3 consists of a temperature-dependent equilibrium mixture of two epimers. When heated or when crystallized one of the epimers is depopulated. The above phenomena and structures are elucidated by an X-ray analysis and by NMR spectroscopy.
    Notes: Distyrylsulfone 1 reagieren mit dem ambidenten Nucleophil Hydroxylamin ausschließlich unter doppelter Addition des Stickstoffs zu 4-Hydroxy-1,4-thiazinan-Derivaten 3. Diese bilden in Lösung temperaturabhängige Epimeren-Gleichgewichte. Sowohl beim Erwärmen als auch beim Auskristallisieren erfolgt Depopulation eines Epimers. Strukturen und Phänomene werden durch Röntgenstrukturanalyse und NMR-Spektroskopie geklärt.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0170-2041
    Keywords: β-Galactosyltransferase ; Glycoproteins, N-linked ; Branch specificity ; Spacer-modified oligosaccharides ; Enzymes ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differentiation of the Branch-Specific Enzymic Galactosylation by Nuclear-Magnetic Resonance SpectroscopyA spacer-modified biantennary trisaccharide glycoside (2) carrying two GlcNAc end groups was galactosylated by UDP-Gal and β-(1→4)-D-galactosyltransferase to yield compounds 3a, 3b and 4. The non-separable monogalactosylated compounds 3a and 3b were investigated by NMR spectroscopy (COSY, COLOC, RELAY) to determine a potential branch-specific transgalactosylation found for native acceptor-oligosaccharides (1). Since the “3-branch” is galactosylated at the same rate as the “6-branch” the presence not only of the center-mannosyl unit but also of the flanking mannosyl residues replaced by spacers in compound 2 are necessary for site specificity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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