Asymmetric Total Synthesis of (+)-21-epi-Eburnamonine Via a Photocatalytic Radical Cascade Reaction.

An asymmetric total synthesis of (+)-21-epi-eburnamonine has been achieved. Key features of the synthesis include a visible-light photocatalytic intra-/intramolecular radical cascade reaction to assemble the tetracyclic ABCD ring system, and a highly diastereoselective Johnson-Claisen rearrangement to establish the C20 all-carbon quaternary stereocenter.

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.