Molecular and crystal structure of prionostemmadione, a new dioxofriedelane from Prionostemma aspera

Abstract

The root bark of Prionostemma aspera contains friedelin and a new C₄₀, diketone, prionostemmadione, shown to be a friedelane derivative from spectroscopic data. One carbonyl group had the properties of a normal 3-oxo-group, and the other, which was not reduced by sodium borohydride, was located at C-12 on mass spectral evidence. The 3,12-dioxofriedelane structure was confirmed by X-ray crystallographic analysis, the crystals having an approximate chair–chair–chair–boat–boat conformation for rings A–E.