6,8-Dihy­droxy-8a-methyl-3,5-dimethyl­idenedeca­hydro­naphtho­[2,3-b]furan-2(3H)-one

The title compound, C(15)H(20)O(4), is a eudesmanolide isolated from the Chinese medicinal plant Carpesium tris­te Maxim. The mol­ecule contains three rings, viz. two fused six-membered rings in chair conformations and a five-membered ring in a flattened envelope conformation. In the crystal, two hy­droxy groups are involved in the formation of intra- and inter­molecular O—H⋯O hydrogen bonds. The H atoms in these groups are split, with site-occupation factors of 0.5. The inter­molecular hydrogen bonds link mol­ecules into chains propagating in [010].