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], C15H22O5, 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 1H 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.