Crystal structure of (1S,2R,4R,9S,11S,12R)-9α-hy-droxy-4,8-dimethyl-12-[(thio-morpholin-4-yl)meth-yl]-3,14-dioxatri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one.

The title compound, C19H29NO4S, was synthesised from 9α-hy-droxy-parthenolide (9α-hy-droxy-4,8-dimethyl-12-methyl-ene-3,14-dioxatri-cyclo-[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 the plant Anvillea radiata. The mol-ecule is built up from two fused five- and ten-membered rings, with an additional ep-oxy ring system and a thio-morpholine group as a substituent. The ten-membered ring adopts an approximate chair-chair conformation, while the thio-morpholine ring displays a chair conformation and the five-membered ring has an envelope conformation, with the C atom closest to the hy-droxy group forming the flap. An intra-molecular O-H⋯N hydrogen bond closes an S(8) ring. The crystal structure features weak C-H⋯O hydrogen-bonding inter-actions, which link the mol-ecules into [010] chains.