10α-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, C(20)H(31)NO(5), was synthesized from 9α-hy-droxy-parthenolide (9α-hy-droxy-4,8-dimethyl-12-methylen-3,14-dioxa-tricyclo-[9.3.0.0(2),(4)]tetra-dec-7-en-13-one), which was isolated from the chloro-form extract of the aerial parts of Anvillea radiata. The mol-ecule 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 intra-molecular O-H⋯N hydrogen-bond occurs. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.