118964-27-5Relevant academic research and scientific papers
STRUCTURE AND SYNTHESIS OF PHLOBATANNINS RELATED TO (-)-FISETINIDOL-(-)-EPICATECHIN PROFISETINIDINS
Steynberg, Jan P.,Burger, Johann F. W.,Cronje, Annemarie,Bonnet, Susan L.,Malan, Johannes, C. S.,et al.
, p. 2979 - 2989 (1990)
Several members of the class of natural 'phlobaphene' condensed tannins, representing the products of C-ring isomerization of (-)-fisetinidol-(4α,8)-(-)-epicatechin profisetinidins have been characterized.These comprise four functionalized tetrahydropyranochromenes, two -analogues and four -regioisomers.A novel protocol of effecting differentiation between the regio-isomers based on homonuclear NOE difference spectroscopy (1H NMR) is proposed.The structures of some of the natural products were confirmed by synthesis via base-catalysed rearrangement of their presumed precursors.Under these mild alkaline conditions, the biflavanoids are susceptible to epimerization at C-2 (F-ring) hence leading to conversion of a (-)-epicatechin to a (-)-catechin DEF moiety.The natural occurence of pyran rearranged analogues related to both these units presumably reflects similar mechanisms for the in vivo and in vitro processes.
