123484-73-1Relevant articles and documents
Oligomeric Flavanoids. Part 5. Base-catalysed C-Ring Isomerization of (+)-Fisetinidol-(+)-catechin Profisetinidins
Burger, Johann F. W.,Steynberg, Jan P.,Young, Desmond A.,Brandt, E. Vincent,Ferreira, Daneel
, p. 671 - 681 (2007/10/02)
The (+)-fisetinidol-(+)-catechin profisetinidins are subject to similar base-catalyzed C-ring isomerizations to the quasi-enantiomeric (-)-fisetinidol-(+)-catechins.Whereas "upper" 2,3-trans-3,4-trans-flavan-3-ol units are susceptible to stereospecific transformations, those species whith a 2,3-trans-3,4-cis-configuration react more rapidly in a stereospecific manner and are furthermore subject to isomerization with concominant interchange of resorcinol A- and pyrocatechol B-rings.These differences are explicable in terms of the effect of configuration at C-4 on both the rate of formation of intermediate B-ring quinone-methides and the recyclization step.This comparative study not only confirms the mechanism of A/B-ring interchange but also reveals serious shortcomings in the c.d. method for defining absolute configuration of phlobatannins with cis-trans and all-trans configuration of their C-rings.