Extending Pummerer Reaction Chemistry: Application to the Assembly of the Pentacyclic Core of Dibromopalau’amine

A pentacyclic model system featuring the trans azabicyclo[3.3.0]octane unit of dibromopalau’amine was prepared with complete diastereoselectivity in the polycyclic core from a tricyclic precursor. The key transformations of this sequence include (a) a Pummerer reaction-mediated oxidative bicyclization, and (b) a Wolff rearrangement-based ring contraction to deliver the strained azabicyclo[3.3.0]octane core.