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Conformational analysis of oligomeric flavanoidsAuthor(s): Jan P. Steynberg; E. Vincent Brandt; Daneel Ferreira; Carin A. Helfer; Wayne L. Mattice; Dominika Gornik; Richard W. Hemingway
Source: Magnetic Resonance in Chemistry 33:611-620
Publication Series: Miscellaneous Publication
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DescriptionThe 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 diastereomersis 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 catechin unit, although mostly in an E-conformation, was often represented by significant proportions of A-conformers.
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CitationSteynberg, Jan P.; Brandt, E. Vincent; Ferreira, Daneel; Helfer, Carin A.; Mattice, Wayne L.; Gornik, Dominika; Hemingway, Richard W. 1995. Conformational analysis of oligomeric flavanoids. Magnetic Resonance in Chemistry 33:611-620
KeywordsNMR, 1H NMR, condensed tannins, profisetinidins, stereochemistry, conformation, rotational isomers
- Conformation analysis of oligomeric flavanoids
- Conformational isomerism of phenolic procyanidins: preferred conformations in organic solvents and water
- Implications of the fluorescence for the conformational analysis of polymeric profisetinidins and procyanidins
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