Total Synthesis of (-)-Aspergilazine A

The total synthesis of (-)-aspergilazine A, an alkaloid possessing a rare N1' to C6 bisindole bond, is described. A palladium-catalyzed N-arylation was used to selectively install the N1'-C6 bond in the presence of three other possible arylation sites. The ligand XPhos displayed a unique capability to efficiently carry out the N-arylation while simultaneously suppressing epimerization of the sensitive C9 stereocenters. This total synthesis has confirmed that aspergilazine A is a dimer of brevianamide F.