Asymmetric Synthesis of an Advanced Tetracyclic Framework of (+)-Sarain A

An asymmetric synthetic approach to a tetracyclic framework of the marine-derived alkaloid (+)-sarain A has been developed. The key steps to constructing the congested diazatricycloundecane core include an asymmetric Diels–Alder cycloaddition, an Ireland–Claisen rearrangement, and an intramolecular aziridination/ring-opening sequence.