An angularly fused three‐ring precursor to phytuberin

The title compound, 3,3a,5,5a,6,7,8,9‐octahydro‐3a‐hydroxy‐5a‐methyl‐8‐(2‐prop­enyl)­furo­3,2‐c]­iso­benzo­furan‐2‐one, C₁₄H₂₀O₄, crystallizes with two independent molecules in the asymmetric unit. The molecules have similar metric parameters but differ in the conformations of the isopropenyl groups. The hydroxyl groups form one‐dimensional chains of hydrogen bonds.