Catalytic enantioselective total syntheses of bakkenolides I, J, and S: application of a carbene-catalyzed desymmetrization.

A general strategy for the catalytic asymmetric syntheses of the bakkenolides is reported. The key bond-forming step involves an N-heterocyclic carbene catalyzed desymmetrization of a 1,3-diketone to form three new bonds in one step with excellent enantio- and diastereoselectivity. This intramolecular reaction allows direct access to the hydrindane core of the bakkenolide family and enables a facile synthesis of these natural products.