Cynaratriol, a sesquiterpene lactone from Centaurea musimomum

The title compound [systematic name: 3,8-dihydr­oxy-3-(hydroxy­meth­yl)-9-methyl-6-methyl­enedeca­hydro­azuleno[4,5-b]furan-2(3H)-one], C(15)H(22)O(5), is a sesquiterpene lactone showing the typical tricyclic guaianolide skeleton which has been isolated, together with other related metabolites, from the plant Centaurea musimomum. The present study confirms the mol­ecular structure, assigned by (1)H NMR and MS spectroscopy, as well as the the 11β-hydroxy­methyl, 3β-hydr­oxy and 4α-methyl stereochemistry. The crystal structure is built through a network of O—H⋯O hydrogen bonds involving the three hydroxyl groups that are present in the mol­ecular skeleton.