Five New Stilbene Dimers from the Lianas of Gnetum hainanense

Abstract
Five new stilbene dimers, gnetuhainins A−E (1−5), were isolated together with resveratrol trans-dehydrodimer (6), resveratrol, oxyresveratrol, and (−)-ε-viniferin from the lianas of Gnetum hainanense. Their structures and stereochemistry were determined on the basis of their chemical and spectral data. Compounds 1−5 are dimers formed by a resveratrol unit and an oxyresveratrol unit and belong to a new type of oligostilbenes polymerized from two different stilbene units.