Asymmetric synthesis of a tricyclic benzofuran motif: a privileged core structure in biologically active molecules

An efficient synthetic strategy for the asymmetric synthesis of a hexahydrodibenzofuran core structure, with a quaternary stereogenic center, emerges by employing a chiral reduction using Corey's (S)-Me-CBS-oxazaborolidine reagent followed by a Mitsunobu reaction to set the stereochemistry. A Pd-mediated intramolecular Heck reaction concludes the tricyclic core structure. Finally, a Pd/C catalyzed reduction yields the target molecule in 21% overall yield over 6 steps.