1,4a-Dimethyl-6-methyl-ene-5-(5,5,6,6-tetra-cyano-2-methyl-cyclo-hex-2-enylmeth-yl)deca-hydro-naphthalene-1-carboxylic acid: a trans-communic acid derivative.

In the search for cancer chemopreventive agents, we have studied the Diels-Alder reaction of trans-communic acid with tetra-cyano-ethyl-ene in the presence of SiO(2) as catalyst. The title cycloadduct, C(26)H(30)N(4)O(2), was obtained in 75% yield. The mol-ecules are arranged in pairs through O-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. Both the fused cyclohexyl rings adopt a chair conformation, whereas the nonfused ring adopts a half-chair conformation.