Total synthesis of (+/-)-frondosin B and (+/-)-5-epi-liphagal by using a concise (4+3) cycloaddition approach

Article abstract of DOI:10.1002/chem.201303273

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. Cycloheptanes: Furfuryl alcohols serve as effective three-carbon dienophiles for a wide range of dienes in stereoselective cycloaddition reactions. This efficient reaction has been used to prepare two cycloheptanoid natural products, offering a conceptually straightforward and short synthetic entry into a biologically interesting class of polycyclic meroterpenoids (see scheme; TFA = trifluoroacetic acid). Copyright