Progress Toward the Total Synthesis of Terpenoid Natural Products: the Neomangicols and the Yohimbine Alkaloids
Progress has been made toward the total synthesis of a diverse array of natural products. Chapter 1 begins by introducing the isolation, bioactivity, and biosynthesis of the neomangicol and mangicol sesterterpenoids. Subsequent to that introduction, a summary of previous synthetic approaches to these natural products is presented. In the third section, our synthetic approaches are detailed, beginning with a first generation synthesis of the ABD tricycle, followed by a description of our revised route to the neomangicol tetracyclic core and our work toward the rearrangement of that core to the mangicol spirocyclic core. This chapter concludes with a summary of our accomplishments in this natural product area and outlines several strategies to achieve the desired rearrangement. The last section also includes our initial studies into the formation of the mangicol core. Preliminary work toward the synthesis of the ABD tricycle was performed by Dr. Brian Pujanauski.
Chapter 2 details our work in the area of the yohimbine alkaloids. It begins with an introduction to these pentacyclic indole-containing natural products, discussing their isolation, proposed biosynthesis and giving a brief overview of the rich bioactivity that has been ascertained for these molecules. Closely related synthetic approaches are also described. Finally, our divergent approach to the synthesis of several yohimbine alkaloids, as well as strategic analogs, is delineated. Our proposal for rendering this route enantioselective is also detailed. This work was done in collaboration with Dr. Terry Lebold and Josh Deitch.