9α-Acet­oxy-1β,10α-ep­oxy­parthenolide

The title compound, C17H22O6, was semi-synthesized from 9-hy­droxy­arthenolide, which was isolated from the chloro­form extract of the aerial parts of Anvillea radiata. The mol­ecule contains fused five- and ten-membered rings: the five-membered lactone ring has a twisted conformation, whereas the ten-membered ring displays an approximate chair–chair conformation. The dihedral angle between the rings is 24.76 (9)°.