4‐Hydroxy‐3,4a,8‐trimethyl‐3,3a,4,4a,7a,8,9,9a‐octahydroazuleno[6,5‐b]furan‐2,5‐dione

The title compound, C15H20O4, also known as dihydro­helenalin, is a drug obtained from a Chinese plant. It contains a seven-membered ring in a chair conformation and two five-membered rings in twist conformations. The crystal packing involves O—H⋯O hydrogen bonds.