4β,15-Dihydro-3-dehydrosolstitialin A.

The sesquiterpene lactone 4β, 15-dihydro-3-dehydrosolstitialin A, C 15 H 20 O 5 , was isolated from Centaurea musimomum, a composite collected in the Souk-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 conformations. The crystal structure is stabilized by intermolecular hydrogen bonds, with O...O separations of 2.709 (3) and 3.007 (2) A.