Wessely oxidation of o-(3-alkenyl) phenols (5) with lead tetraacetate gives 6-acetoxy-6-(3- alkenyl)-2, 4-cyclohexadien-1-ones (6), which undergo intramolecular Diels-Alder reactions to give isotwistene (hexahydro-1, 5-methanoindene) derivatives (7). These, on hydrolysis followed by oxidation with periodic acid, give hexahydro-1-oxo-1 H-indene-5-carboxylic acids (41, 46). Compounds 5 were prepared either by Grignard coupling of o- ...