Rotational isomerism of a resveratrol tetramer, shoreaketone, in Shorea uliginosa

A new resveratrol tetramer, shoreaketone, was isolated from the stem bark of Shorea uliginosa (Dipterocarpaceae). The structure and the relative configuration were confirmed on the basis of 1D- and 2D-NMR spectral data. The structure has a novel framework of fused heptacyclic ring system including an α,β-unsaturated carbonyl group. In NMR spectra, shoreaketone is observed as two different conformers due to rotational isomerism.