Methyl 3,3,6,6-tetra-methyl-1,8-dioxo-4,5,7,9-tetra-hydro-2-xanthene-9-carboxyl-ate.

The title mol-ecule, CHO, is built by annulation of a half-chair cyclo-hexenone and a twist-cyclo-hexenone to a flat 4--pyrane boat. In the crystal, mol-ecules are connected van der Waals inter-actions and C-H⋯O hydrogen bonds.