A novel approach for construction of the naturally occurring dihydroagarofuran sesquiterpene skeleton

A general and efficient approach for the synthesis of a kind of dihydrofuran sesquiterpenes extensively present in the Celastraceae family of plants has been developed by a series of transformations from santonin. The key creative and versatile steps involve the strategic acid-catalyzed double-bond shifting affording 6, the novel base-promoted epoxide rearrangement of 7 generating two key functions (the C5-OH and the Δ^7,11 double bond) and the stereoselective construction of a tetrahydrofuran moiety without particularly controlling the stereochemistry of C7. In particular, this approach can introduce any number of hydroxyls at the required positions for synthesis of many natural dihydroagarofuran sesquiterpenes.