Galloylhamameloses and proanthocyanidins from Hamamelis virginiana

The unique series of C-1 acylated galloylhamameloses is extended by the discovery of 1-O-(4-hydroxybenzoyl)-2',3,5-tri-O-galloyl-alpha-D-hamamelofuranose and its 1-O-beta-anomer. They are accompanied by the parent 2',3,5-tri-O-galloyl-D-hamamelofuranose and the first pyranose analogue, shown to be 2',4-di-O-galloyl-D-hamamelopyranose. Assignment of H-1 NMR data for the peracetates of hamamelitannin is revised on the basis of a NOESY experiment. Structural examination of the proanthocyanidins present in the bark of Hamamelis virginiana reveals the occurrence of the novel epicatechin-(4 beta --> 8)-catechin-3-O-(4-hydroxy)benzoate, the uncommon prodelphinidins, epigallocatechin-(4 beta --> 8)-catechin, 3-O-galloyl epigallocatechin-(4 beta --> 8)-catechin and 3-O-galloyl epigallocatechin-(4 beta --> 8)-gallocatechin, together with the procyanidins, 3-O-galloyl epicatechin-(4 beta --> 8)-catechin and catechin-(4 alpha --> 8)-catechin, and a tentatively characterized oligomer. The structures of these compounds were established by chemical and spectroscopic methods.