SYNTHETIC STUDIES ON THE INGENANE DITERPENES - CONSTRUCTION OF A TETRACYCLIC 8-ISOINGENANE MODEL

A thermally allowed tropone-diene [6pi + 4pi] cycloaddition is employe d to produce a functionally rich BC ring building block for the constr uction of 8-isoingenol intermediates. Bridgehead enolate alkylation fo llowed by aldol condensation is used to install the elements of the A- ring. Stereo- and regioselective bis-hydroxylation at C-13 and -14 of the C-ring followed by activation as the corresponding bis-mesyloxy de rivative and treatment with diethyl sodiomalonate affords an advanced, functionalized isoingenol tetracyclic intermediate.