Curcumenol from Curcuma zedoaria: a second monoclinic modification.

The title compound, systematic name 9-isopropyl-idene-2,6-dimethyl-11-oxatricyclo-[6.2.1.0(1,5)]undec-6-en-8-ol, C(15)H(22)O(2), which crystallizes with two mol-ecules of similar conformation in the asymmetric unit, features three fused rings, two of which are five-membered and the third six-membered. Of the two five-membered rings, the one with an O atom has a distinct envelope shape (with the O atom representing the flap). The six-membered ring is also envelope-shaped as it shares a common O atom with the five-membered ring. In the crystal, the two independent mol-ecules are linked by a pair of O-H⋯O hydrogen bonds, generating a dimer.