OLIGOMERIC PROANTHOCYANIDINS POSSESSING A DOUBLY LINKED STRUCTURE FROM PAVETTA-OWARIENSIS

Pavetannins B7 and B8, two new trimeric proanthocyanidins, have been isolated from the stem bark of Pavetta owariensis, along with the known tetramers cinnamtannin B2 and its positional isomer, pavetannin C1, and the pentamer pavetannin D1. NMR and mass spectral data established the structure of the pavetannins as epicatechin-(4 beta --> 8, 2 beta --> O --> 7)-ent-epicatechin-(4 alpha --> 8, 2 alpha --> O --> 7)-ent-catechin, epicatechin-(4 beta --> 8, 2 beta --> O --> 7)-epicatechin-(4 beta --> 8; 2 beta --> O --> 7)-ent-catechin, epicatechin-(4 beta --> 6)-epicatechin-(4 beta --> 8, 2 beta --> O --> 7)-epicatechin-(4 beta --> 8)-epicatechin and epicatechin-(4 beta --> 8)-epicatechin-(4 beta --> 8, 2 beta --> O --> 7)-epicatechin-(4 beta --> 8)-epicatechin-(4 beta --> 8)-epicatechin, respectively. The naming of cinnamtannin B2 is revised to epicatechin-(4 beta --> 8)-epicatechin-(4 beta --> 8,2 beta --> O --> 7)-epicatechin-(4 beta --> 8)-epicatechin, according to its structural presentation.