STRUCTURE OF DIETHYL 1,2,3,3B,4A,5,6,7,8,8A,8B,9-DODECAHYDRO-1,5-DIOXO-4,8,9-METHENO-4H-CYCLOPENTA(1,2-ALPHA 4,3-ALPHA')DIPENTALENE-4,10-DICARBOXYLATE

C24H24O6, M(r) = 408.45, triclinic, P1BAR, a = 10.276 (2), b = 13.000 (2), c = 7.782 (1) angstrom, alpha = 98.06 (1), beta = 97.63 (1), gamma = 84.43 (1)-degrees, V = 1017 angstrom-3, Z = 2, D(x) = 1.33 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 0.89 cm-1, F(000) = 432, T = 296 K, R = 0.048 for 3321 unique reflections with F(o)2 > 3-sigma(F(o)2). Both cyclopentenones are canted in the endo direction (6.0 and 7.9-degrees), the one syn to the ethoxy groups less so for steric reasons. When the ester groups are disregarded, the polyquinane portion of the molecule is seen to possess a non-crystallographic twofold axis. The overall molecular geometry is reconcilable with the absence of any significant alteration in the density maximum of the C-C pi-bonds at this level of downward pyramidalization.