The long-term goal of our research program is to develop general and selective nitrogen atom transfer methods that can generate new molecular entities through precise functionalization of both complex molecules and simple commodity chemicals. A large number of therapeutic molecules and small-molecule biological probes have at least one nitrogen atom; therefore, synthetic methods based on direct nitrogen atom transfer to organic molecules are important synthetic tools. Although a variety of valuable olefin amination methods have been established, new selective nitrogen atom transfer methods based on novel reaction mechanisms are still urgently needed which can be effective and exquisitely selective across a broad range of substrates and thereby fill important gaps of existing synthetic approaches. Inspired by these outstanding synthetic challenges, we intend to discover new reactivity in three directions of selective nitrogen atom transfer and we will develop new synthetic methods that hold the promise to become unique and enabling tools for organic synthesis and medicinal chemistry. First, we will explore uncharted territory in iron catalysis and discover the iron-catalyzed olefin amination that does not involve radical intermediates and would thereby be compatible with a range of functional groups which are problematic with the alternative amination methods. Completion of this project will provide effective methods for selective olefin amination in complex molecules. Next, we will discover a fundamentally new cis-glycosylation reaction that does not proceed through an oxocarbenium ion and develop a series of iron-catalyzed one-step glycal amidoglycosylation methods that efficiently connect glycals and glycosyl acceptors to selectively afford 1,2-cis-amido glycosidic linkages that are known to be difficult to form reliably in high stereoselectivity using traditional glycosylation methods. Completion of this project will provide an array of unique methods that fill an important gap in complex-carbohydrate synthesis. Furthermore, we will explore an entirely new HN3 activation mechanism and develop a range of metal-free methods that enable direct addition of HN3 at ambient temperature across a wide variety of unactivated olefins for azido-group labeling of complex molecules. Completion of this project will provide a valuable tool of azido-group labeling for applications in synthetic chemistry and chemical biology.
Numerous therapeutic molecules and small-molecule biological probes are synthetic agents and many of them contain at least one nitrogen atom; therefore, the subject of this proposal?discovery of novel synthetic methods for efficient synthesis of these nitrogen- containing molecules will advance drug discoveries as well as the basic biomedical and clinical research.