9β-Hydroxy-6,9-dimethyl-3-methylene-3a,4,8,9,9a,9b-hexahydroazuleno[4,5-b]furan-2(3H)-one

The title compound, C15H18O3, was synthesized from 9α-hydroxyparthenolide (9α-hydroxy-4,8-dimethyl-12-methylen-3,14-dioxa-tricyclo[9.3.0.02,4]tetradec-7-en-13-one), which was isolated from the chloroform extract of the aerial parts of Anvillea radiata. The seven-membered ring of the title compound shows a chair conformation, while the five-membered rings exibit different conformations, viz a twisted one for the lactone ring and an envelope conformation for the other five-membered ring with the C atom closest to the hydroxy group forming the flap. In the crystal, O—H⋯O hydrogen bonds connect molecules into dimers that are interconnected by C—H⋯O interactions, producing supramolecular chains along the b axis.