10[alpha]-Hy­droxy-4,9-dimethyl-13-(pipyridin-1-ylmethyl)-3,8,15-trioxatetra­cyclo­[10.3.0.02,4.07,9]tetra­decan-14-one

The title compound, C20H31NO5, 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 molecule is built up from fused five-and ten-membered rings with the pipyridin-1-yl-methyl group as a substituent. The ten-membered ring adopts an approximate chair–chair conformation, while the six- and five-membered rings display chair and envelope conformations, respectively. The dihedral angle between the mean planes of the ten-membered ring and the lactone ring is 20.8 (3)°. An intramolecular O—H...N hydrogen-bond occurs. The crystal structure is stabilized by weak intermolecular C—H...O hydrogen bonds.