6,6′-Dioxo-2,2-bi(7-oxatri­cyclo­[3.2.1.13,8]­nonane)-4,4′-di­carboxyl­ic acid

The title mol­ecule, C18H18O8, has C2 molecular symmetry. In the crystal structure, each mol­ecule is connected to four neighbours via intermolecular O—H⋯O hydrogen bonds to form a two-dimensional network parallel to (100).