7-Meth-oxy-penta-cyclo-[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undec-ane-8,11-dione.

The structure of 7-meth-oxy-penta-cyclo-[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane-8,11-dione, C 12 H 12 O 3 , at 150 K has monoclinic ( P 2 1 / c ) symmetry. The penta-cyclo-undecane cage compound is composed of four five-membered rings, a planar four-membered ring and a six-membered ring in a boat conformation fused into a closed strained-cage framework. All of the five-membered rings adopt an envelope conformation.