Two novel trimeric resveratrol derivatives from Cotylelobium lanceolatum.

Two new resveratrol (= 5-[(E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol) trimers, cotylelophenols A (1) and B (2), were isolated from the stem of Cotylelobium lanceolatum (Dipterocarpaceae), together with ten known resveratrol oligomers (3-12). The structures of the isolates were established on the basis of spectroscopic analyses, including a detailed NMR spectroscopic investigation of 1 under different conditions. Compound 1 is the first resveratrol trimer with a rearranged 4-hydroxyphenyl group. Four possible biogenetic pathways towards resveratrol oligomers are proposed (Scheme).