Synthetic Studies in the Terpene Field

Part I. Synthetic Approaches to B-Vetivone A stereoselective synthetic route to the beta-vetivone structure (proposed by Pfau and Plattner) from a bicyclo[3,2,2]nonene derivative has been investigated. Anti-3-exo-benzoyloxybicyclo[3,2,2]non-8-ene-6,7-endo-dicarboxylic acid anhydride, obtained after a detailed investigation of the Diels-Alder reaction of cyclohepta-3,5-dienol derivatives with maleic anhydride, has been elaborated in nine stages to 4-amino-3-cyano-9,9-ethylenedioxytricyclo[5,3,2,0 2,6]dodeca-3,11-diene (endo configuration) via 3,3-ethylenedioxy-6,7-endo-dicarbomethoxybicyclo[3,2,2]non-8-ene. Appendix (with F. A. Cameron and G. Ferguson) The major product from the Diels-Alder reaction of maleic anhydride with 1-p-bromobenzoyloxycyclohepta-3,5-diene is shown by an X-ray structure determination to be the anti-3-exo configuration. Part II. N. M. R. Studies of some Bicyclo[3.2.2]nonene Derivatives: An N. M. R. comparative study of sixteen bicyclo[3,2,2]nonene derivatives (prepared in Part I) has indicated that the endo configuration of substituents. at and can be assigned unambiguously. Tentative proposals concerning the conformational stability of the three carbon bridge are put forward. Part III. Synthetic Approaches to a Diterpene Intermediate Two routes to 10-alkoxy-5-methyltricyclo [7,2,1,0 1,6] dodeca-4,12-dione as a precursor to tetracyclic diterpenes, have been investigated. The synthesis of 9-carbethoxymethylene-5-methyl- 5,10-octalin-1,6-dione and the derived hydrogenation products are described. The mechanism of a novel rearrangement of 2-carbethoxymethylene-2-(3 '-ketopentyl)cyclohexane-1,3-dione and other 2,2-disubstituted cyclohexane-1,3-diones to substituted valerolactone derivatives is described