| The neolignans are a diverse group of plant metabolites that contain the dihydrobenzofuran moiety as a key structural element. A biomimetic reductive intramolecular cyclization process has been developed to synthesize dihydrobenzofurans. Detailed study of a mild acid catalysed cyclization of various β-hydroxyethylquinone precursors in the presence of 1,4-dihydrobenzoquinone, functioning as a reducing agent, has been described. The effects of the reducing agent, the stoichiometries of the acid and the various substituents on the quinones on the outcome of the cyclization are discussed. This mild route to dihydrobenzofurans using a reagent based electrochemical transformation has then been successfully applied to the total synthesis of a naturally occurring neolignan (±) obtusafuran.; The decalin ring system is a core structural unit in a variety of biologically important natural products, such as arenols and clerodanes. These classes possess either a cis- or trans-fused decalin ring system as well as a characteristic 9-alkyl and an 8,9-dimethyl vicinal arrangement. A concise approach to these systems using a Lewis-acid catalysed Diels Alder reaction, where the 8,9-dimethyl syn arrangement has been set previously, is demonstrated. An efficient and stereocontrolled preparation of appropriately functionalized dienes, which can be further elaborated into the desired Diels Alder precursors, has been carried out using achiral 3,4-dimethoxy cyclopentenone. |
