STRUCTURE AND SYNTHESIS OF PHLOBATANNINS RELATED TO THE (4-BETA,6-4-ALPHA,8)-BIS-FISETINIDOL-CATECHIN PROFISETINIDIN TRIELAVANOID

Several members of the class of natural phlobatannins, representing th e products of stereoselective pyran rearrangement of the 2,3-trans-3,4 -trans- and 3,4-cis-flavan-3-ol units in the (4 beta,6:4 alpha,8)-bis- fisetinidol-catechin triflavanoid have been characterized. These compr ise a functionalized hexahydro-dipyrano-[2,3-f:2',3'-h]-chromene, two fisetinidol-(4 alpha,10)-tetrahydropyrano[2,3-f]chromenes and a pair o f fisetinidol-(4 alpha,10)-tetrahydropyrano[3,2-g]chromenes. The propo sed structures of these novel compounds were confirmed by synthesis vi a base-catalysed conversion of the 4-O(E)-methyl ether of their presum ed triflavanoid biogenetic precursor. Copyright (C) 1996 Elsevier Scie nce Ltd