2,6-Dioxa-3,7-dioxotricyclo[3.3.3.01,5]undecane, a Propellanoid Dilactone Representing a New Tricyclic Ring System

The title material, tetrahydro-3a,6a-propanofuro-3,2-b]furan-2,5-dione (C₉H₁₀O₄), is a new compound representing a previously unreported ring system. Its asymmetric unit lacks an axis of symmetry because of nonplanarity in the carbon ring. Although the bulk material is racemic, only single enantiomers are incorporated into the crystal, which is unusually dense. Several intermolecular C–H O close contacts were found.