Molecular Complexity from Aromatics: Synthesis and Photoreaction of endo-Tricyclo[5.2.2.02,6]undecanes. Formal Total Syntheses of (±)-Coriolin

Formal syntheses of coriolin 1, a triquinane metabolite isolated from Coriolus consors, are described. Oxidation of 6-methyl saligenin 2 in the presence of cyclopentadiene gave the tricyclic keto epoxide 4 which was elaborated to tricyclo[5.2.2.02,6]undecenones 5 and 18 containing the major structural and stereochemical features of coriolin, in latent form. Triplet sensitized 1,2-acyl shifts in 5 and 18 gave tetracyclic compounds 6 and 19 in a stereoselective manner. Reductive cleavage of cyclopropane rings in 6 and 19 with H2/Pd-C and TBTH-AIBN respectively, furnished the functionalised triquinanes 7 and 20b which are known precursors for coriolin.