Flavans and A-type proanthocyanidins from Prunus prostrata

A new natural dimeric A-type proanthocyanidin and two new monomeric flavanols have been isolated from Prunus prostrata and identified as ent-epiafzelechin (2 alpha-->O-->7, 4 alpha-->8) quercetin, 5,7,2',5'-tetrahydroxy-(2R,3R)-flavan-3-ol and, 7-methoxy-(+)-catechin, respectively. The structurally related metabolites ent-epiafzelechin (2 alpha-->O-->7, 4 alpha-->8) afzelechin, ent-epiafzelechin (2 alpha-->O-->7, 4 alpha-->8) kaempferol, ent-epiafzelechin (2 alpha-->O-->7, 4 alpha-->8) epicatechin, ent-epiafielechin (2 alpha-->O-->7, 4 alpha-->8) epiafzelechin, ent-epiafzelechin (2 alpha-->O-->7, 4 alpha-->8) catechin, (+)-catechin and (-)-epicatechin were also isolated. Structure elucidation was achieved by extensive NMR (home- and hetero-nuclear two-dimensional correlation, NOE difference, and selective INEPT experiments) and CD studies. Copyright (C) 1996 Elsevier Science Ltd.