Abstract
The application of high resolution 1H-NMR and empirical (MM2, MMX) as well as semiempirical (MNDO, AMI, PM3) theoretical methods in the conformational analysis of proanthocyanidins have been the subject of much study. The E:A (B-ring equatorial or axial) ratios calculated for 4-arylflavan-3-ol model compounds, carefully selected to incorporate all relevant structural parameters, were implemented to analyze the steric forces that control the puckering of the flavan heterocyclic ring. These results show that the delicate equilibrium between E- and A-conformers is controlled by A(1,3)-strain and 1,3-diaxial interactions.
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Steynberg, J.P., Brandt, E.V., Hoffman, M.J.H., Hemingway, R.W., Ferreira, D. (1992). Conformations of Proanthocyanidins. In: Hemingway, R.W., Laks, P.E. (eds) Plant Polyphenols. Basic Life Sciences, vol 59. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-3476-1_29
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DOI: https://doi.org/10.1007/978-1-4615-3476-1_29
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