Synthesis of modified proanthocyanidins:: introduction of acyl substituents at C-8 of catechin.: Selective synthesis of a C-4→O→C-3 ether-linked procyanidin-like dimer

The regioselective introduction of substituents at C-8 of (+)-catechin is described, leading to the synthesis of several catechin derivatives with various substitution patterns to be used for the further synthesis of modified proanthocyanidins. Thereafter, a new 3-O-4 ether-linked procyanidin-like derivative was synthesized. Its formation was selectively achieved through TiCl4-catalyzed condensation of 4-(2-hydroxyethoxy)tetra-O-benzyl catechin with the 8-trifluoroacetyl adduct of tetra-O-benzyl catechin. (C) 2004 Elsevier Ltd. All rights reserved.