2,4-Dioxa-λ(6)-thia-tetra-cyclo-[5.3.1.1(5,9).0(1,5)]dodecane-3,3-dione.

The crystal structure of the title compound, C(9)H(12)O(4)S, was determined in order to investigate the effect of the eclipsed O atoms on the bond length of the vicinal quaternary C atoms. The two quaternary C atoms of the noradamantane skeleton and the two O atoms to which they are connected all located essentially in the same plane (maximum deviation = 0.01 Å), resulting in an eclipsed conformation of the C-O bonds. The C-C bond of the quaternary C atoms is 1.581 (3) Å, considerably longer than the other C-C bonds of the mol-ecule due to the stretch of the cage structure.