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  • 1
    Electronic Resource
    Electronic Resource
    Implications of the fluorescence for the conformational analysis of polymeric profisetinidins and procyanidins (1995)
    Springer
    Polymer bulletin 34 (1995), S. 79-85 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The common monomeric units in the polymeric procyanidins are catechin and epicatechin, which have a hydroxyl group at C(5). This hydroxyl group is absent in the profisetinidins. The fluorescence properties have been characterized for the profisetinidin monomer and dimers, and compared with previous results for the procyanidins. There is a measurable heterogeneity in the fluorescence of fisetinidol, in contrast to the simpler fluorescence of the procyanidin monomers. This heterogeneity is attributed to differences in the photophysical properties of the aromatic A- and B-rings in fisetinidol. These differences are larger in fisetinidol than in catechin or epicatechin. The heterogeneity prevents determination by fluorescence of the conformations at the interflavan bond in the profisetinidins by the data analysis employed successfully with the procyanidins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294891
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  • 2
    Electronic Resource
    Electronic Resource
    Crystal structure, conformational analysis, and molecular dynamics of tetra-O-methyl-(+) -catechin (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 275-282 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of tetra-O-methyl- (+) -catechin has been determined in the crystalline state. Two independent molecules, denoted structure A and structure B, exist in the unit cell. Crystals are triclinic, space group P1, a = 4.8125(2) Å, b = 12.9148(8) Å, c = 13.8862(11) Å, α = 86.962(6) °, β = 89.120(5)°, γ = 88.044(5)°, Z = 2, Dc = 1.336 g cm-3, R = 0.033 for 6830 observations. The heterocyclic rings of the crystal structures are compared to previous results for 8-bromotetra-O-methyl-(+)-catechin, penta-O-acetyl-(+)-catechin, and (-) -epicatechin. One of the two molecules has a heterocyclic ring conformation similar to that observed previously for (-)-epicatechin, and the other has a heterocyclic ring conformation similar to one predicted earlier in a theoretical analysis of dimers of (+)-catechin and (-) -epicatechin. Both structure A and structure B in the crystal have heterocyclic ring conformations that place the dimethoxyphenyl substituent at C(2) in the equatorial position. However, this heterocyclic ring conformation does not explain the proton nmr coupling constant measured in solution. Molecular dynamics simulations show an equatorial ⇌ axial interconversion of the heterocyclic ring, which can explain the nmr results. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330209
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational analysis of oligomeric flavanoids. 2For Part 1, see Ref. 8. - methyl ether acetate derivatives of profisetinidins (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 611-620 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; condensed tannins ; profisetinidins ; stereochemistry ; conformation ; rotational isomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The profisetinidins are the most important polyflavanoids of commerce, making up the major constituents of wattle and quebracho tannins. Even within the dimeric profisetinidins, substantial complexity exists because of stereo-, regio-, rotational and conformational isomers. Definition of the stereochemistry of the upper and lower flavan units, the location of the interflavanoid bond, the conformation of the heterocyclic rings in the upper and lower flavan units and the conformations of major and minor rotational isomers in a series of methyl ether acetate derivatives of dimeric profisetinidin diastereomers is possible by application of COSY and NOE experiments. All compounds studied were present in two rotameric forms with the more compact conformation favored. The heterocyclic ring in the upper chain extender unit was predominantly in an E-conformation (i.e. half-chair in 2R,3S isomers and a ‘reverse’ half-chair in the 2S,3R isomers). The heterocyclic ring conformation of the terminal cate-chin unit, although mostly in an E-conformation, was often represented by significant proportions of A-conformers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330802
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