In the title compound, C13H16O4, the cyclohexene rings adopt a sofa conform
ation. Adjacent molecules are connected by C-H . . . O intermolecular inter
actions. Each molecule is characterized by O-H . . . O intramolecular hydro
gen bonds. The anti arrangement of the enolic OH group and the carbonyl O a
tom in the solid state is similar to the anti arrangement of the NH and car
bonyl groups in indigo.