Rhoiptelenyl acetate, a new pentacyclic triterpenoid from Ficus thunbergii

Rhoiptelenol, (2), isolated from Ficus thunbergii Maxim. (Moraceae), has been reported as a triterpenoid component. The title compound, (1), whose molecular formula was shown by its high-resolution mass spectrum to be C 32 H 52 O 2 , was obtained from (2) by acetylation with Ac 2 O and pyridine. The structure of (1) was proved by NMR spectroscopy to be one of a rearranged ursane-type triterpenoid with five six-membered rings. We have described the conformation and geometry of (1) by an X-ray crystallographic analysis and molecular-mechanics calculations.