The structure of 7-methoxypentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione, C12H12O3, at 150 K has monoclinic (P21/c) symmetry. The pentacycloundecane 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.
