2,4-Dioxa-λ-6-thiatetracyclo-[5.3.1.15,9. 01,5]dodecane-3,3-dione

The crystal structure of the title compound, C9H 12O4S, 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 molecule due to the stretch of the cage structure.