(4R)-3-Hy-droxy-7-isopropyl-4-methyl-5,6-di-hydro-benzo-furan-2(4H)-one.

In the title compound, alternatively called α-hy-droxy-γ-alkyl-idenebutenolide, C12H16O3, two independent mol-ecules (A and B) crystallize in the asymmetric unit in each of which the 5,6-di-hydro-benzo ring has an envelope conformation. The torsion angle along the butadiene chain in the γ-alkyl-idenebutenolide core is -177.9 (2)° for mol-ecule A and 179.9 (2)° for mol-ecule B. In the crystal, O-H⋯O hydrogen bonds between hy-droxyl and carbonyl groups of adjacent independent mol-ecules form dimers with R (2) 2(10) loops.