The sesquiterpene lactone 4 beta,15-dihydyo-3-dehydrosolstitialin A, C15H20
O5, was isolated from Centaurea musimomum, a composite collected in the Sou
k-Ahra area in the east of Algeria. The fused-ring system contains a seven-
membered ring in a twisted-boat and two five-membered rings with envelope c
onformations. The crystal structure is stabilized by intermolecular hydroge
n bonds, with O ... O separations of 2.709(3) and 3.007 (2) Angstrom.