GENERAL-APPROACH FOR THE SYNTHESIS OF POLYQUINENES VIA THE WEISS REACTION .15. SYNTHESIS OF THE [5.5.5.5]FENESTRANE SYSTEM VIA THE ALDOL APPROACH AND STUDIES DIRECTED TOWARD THE [5.5.6.6]FENESTRANES

The all cis-8a,12b-diacetoxytetracyclo[5.5.1.0.(4,13)0(10,13)]tridecane-2,6-dione 9 was successfully synthesized via aldolization of the diketodialdehyde 8 under conditions of equilibration, followed by trapping with acetic anhydride. Aldol cyclization of the dialdehyde 14 to provide the [5.5.6.6]fenestrane system 12 was also attempted. This resulted in the observation of tetracycle 25 with the desired ring system albeit as a minor product. The major products isolated from this approach were the undesired alpha,beta-unsaturated aldehyde 22 and monoaldehyde 23, the latter of which contained a configuration opposite to that of C-5 in 12. In addition, the related bisacylation approach provided 26 as the major product with the undesired configuration at C-8. This cyclization furnished the transannular tetraone 27 at higher temperature.