A new α-methylene γ-lactone sesquiterpene from Hedyosmum arborescens

A new sesquiterpene lactone, 7α,10α-epoxy-1α(H),5α(H)-guaia-3,11(13)-dien-8α,12-olide, was isolated from the leaves of Hedyosmum arborescens. The structure of this unusual 7,10-epoxy-guaianolide was determined by spectroscopic methods, particularly one- and two-dimensional 1H and 13C NMR.