The Design and Implementation of Asymmetric Organocatalysis in Synthesis

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DESCRIPTION (provided by applicant): The aims of the proposed research are to develop asymmetric organocatalytic methods for use in synthesis. Recent advances in this area highlight the utility of small organic molecules for promoting synthetic transformations in an efficient and selective manner. Continued progress in the field of organocatalysis will provide access to novel, highly functionalized chiral building blocks in enantioenriched form that have been previously unavailable. The projects in this proposal will concentrate on identifying and exploring chiral Bronsted acid catalysis and chiral base catalysis in order to develop new organocatalytic methods applicable to the synthesis of novel chiral building blocks. We have developed the first highly enantioselective Morita-Baylis-Hillman (MBH) reaction involving enones and aldehydes catalyzed by a small chiral molecule. The reaction achieves high levels of enantioselectivity from an organic catalyst through hydrogen bonding. Mechanistic investigations allow us to apply what we have learned about the MBH reaction to expand the scope and utility of the reaction. Projects in this grant will develop the reaction for use in the synthesis of complex natural products such as the asmarine class of clerodane natural products, potent antiproliferative agents with unknown modes of action which inhibit small cell lung carcinoma growth in nanomolar concentrations. We will also continue to develop the asymmetric MBH reaction for the synthesis of the pycnanthuquinones, orally bioavailable natural products with a unique mode of overcoming the symptoms of type 2 diabetes mellitus. These natural products are unlike other known treatments of type 2 diabetes and will be used to identify the molecular target. We have also successfully developed the asymmetric Mannich reaction of ?-keto esters to acyl imines catalyzed by the cinchona alkaloid class of natural product organocatalysts. Through further investigations, we will expand the scope of the reaction to produce highly functionalized building blocks that can be used for Pharmaceuticals such as the melanin concentrating hormone receptor antagonist SNAP-7941 and the batzellidine natural products. We have also developed the first asymmetric allylboration of carbonyl containing compounds catalyzed by a simple organic compound. The asymmetric reaction will be highlighted in the synthesis of the natural product manzacidin A.