Synthetic Studies in the Formation of Nitrogen Containing Compounds: From Simple Amines to Complex Natural Products
Nash, Aaron Richard
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Small nitrogen containing compounds are important building blocks in synthetic chemistry. Not only for biologically active small molecules but in more complex biologically active natural products. Having novel methods to access these types of molecules is an important undertaking in synthetic chemistry. Then striving to apply these methods to total synthesis of complex natural products is a goal for numerous synthetic studies. First we will discuss the development of a method for the synthesis of unnatural cyclic amino acids. Using a previously developed palladium catalyzed tandem allylic amination/[2,3]-Stevens Rearrangement we were able to access unsaturated amino esters diastereoselectively. These could easily be converted to the desired azepane using a ruthenium catalyzed ring-closing metathesis reaction. Utilizing Oppolzer's chiral auxiliary we could use this method to access enantioenriched free amino acids. Secondly we will discuss the progress toward the use of Frustrated Lewis pairs for the synthesis of chiral benzylic amines. Frustrated Lewis pairs have shown the ability to activate inert bonds such as H-H bonds mildly and selectively. Using these concepts as inspiration we attempted to activate C-H and C-C bonds for the synthesis of chiral amine compounds. Using imines in the presences of various coupling partners we attempted to synthesize benzylic amines and pyrrolidines. Finally, we will discuss our total synthesis of (±)-Lundurine A via vinylogous Pictet-Spengler reaction and our progress toward the catalytic asymmetric vinylogous Pictet-Spengler reaction. The Lundurines are an interesting class of indole containing alkaloids that have shown biological activity. Although there are completed total syntheses of this family of natural products, their uniqueness makes them interesting synthetic targets. Our lab was able to develop a Lewis acid assisted vinylogous Pictet-Spengler reaction that was utilized in the total synthesis (±)-Lundurine A. We continued our studies of this interesting methodology in an attempt to develop a catalytic asymmetric vinylogous Pictet-Spengler Reaction.