Tthe structure of the title compound, C15H24O5, has been redetermined at 103 (2) K, with much improved precision. The title compound was first reported by Luo, Yeh, Brossi, Flippen-Anderson & Gillardi [Helv. Chim. Acta (1984). 67, 1515–1522]. It is a derivative of the antimalaria compound artemisinin and consists primarily of three substituted ring systems fused together. A cyclohexane ring (with a distorted chair conformation), is fused to a tetrahydropyran group (also with a distorted chair conformation), and is adjacent to an oxacycloheptane unit containing an endoperoxide bridge. This gives the molecule a unique three-dimensional arrangement. The crystal packing is stabilized by intermolecular C–H⋯O and O–H⋯O interactions between an H atom from the cyclohexane ring and an O atom from the endoperoxide bridge, as well as between the hydroxyl H atom and an O atom from a tetrahydropyran ring.