Two New Ketonic Resveratrol Tetramers from Shorea platyclados

Two new ketonic resveratrol tetramers, shoreaplatyclaphenols A (1) and B (2), two known resveratrol tetramers (grandiphenol B and hopeaphenol A), and a known trimer resveratrol (α-viniferin), have been isolated from an acetone extract of the tree bark of Shorea platyclados (Dipterocarpaceae). Structure elucidation, including relative configurations, of the new compounds was determined on the basis of spectroscopic evidence, mainly with NMR and mass spectral data. Biogenetic relationship of the resveratrol tetramers isolated in S. platyclados and their chemotaxonomic significance is briefly discussed.