Project description:The title compound, C(15)H(20)O(3), a sesquiterpene lactone, was isolated from the aerial parts of Carpesium minus Hemsl. (Compositae). The mol-ecule is composed of three rings, with the two cyclo-hexane rings in chair conformations and the cyclo-pentane ring adopting a twist conformation. The A/B ring junction is trans-fused. The absolute configuration shown has been arbitrarily assigned. In the crystal, mol-ecules are linked into [100] chains by O-H?O hydrogen bonds.