ABSTRACT
A stereoselective synthetic method is reported for the molecular framework found in common daucane and isodaucane sesquiterpenoid natural products. The synthetic method constitutes a scalable, modular, and also asymmetric access to a complex natural product scaffold, wherein the substitution pattern and the stereochemistry can be adjusted simply by choosing different starting materials. The method allows the rapid introduction of diverse heterocyclic substructures such as (benzo)furans, (benzo)thiophenes, dithiins, thiazoles, and indoles, which actually also facilitate and direct the key intramolecular annulation step.
ABSTRACT
A recently developed (4+3) cycloaddition between dienes and furfuryl alcohols, as precursors of oxyallyl-type cations, has been used as a key step in the racemic syntheses of two natural products: frondosin B and liphagal. This work demonstrates the synthetic potential of this cycloaddition reaction, and offers a short synthetic route to an interesting family of natural products. A full account of these synthetic studies is presented, further illustrating the mechanism, scope, and limitations of this straightforward synthetic method for seven-membered rings.