Total Synthesis of Haliclonacyclamine C

Abstract

Marine natural products have attracted the attention of chemists and biologists across the world for over the past five decades. The fascinating array of marine secondary metabolites has resulted in extensive examination of sponges and tunicates as a source for unique molecular structures as potential novel therapeutics. The 3-alkylpiperidines are a growing subset of natural products that are hypothetically derived from nicotinic acid and isolated from various marine organisms. These alkaloids can be further categorized based on molecular complexity, increasing with incorporation of tricyclic, tetracyclic, and pentacyclic structural motifs. A number of elegant synthetic approaches to access these alkaloids have been reported. However, little progress has been made toward the synthesis of the tetracyclic 3-alkylpiperidines. The theme of this dissertation will emphasize the synthetic details and strategy associated with the total synthesis of the tetracyclic 3-alkylpiperidine alklaloid haliclonacyclamine C. The focus of Chapter I will include isolation, biosynthetic proposals, and biomimetic approaches to the 3-alkylpiperidine alkaloids. Chapter II spotlights purely synthetic approaches to some of the more complex systems within this class of natural products. Chapter III will discuss the isolation, biological activity, and structure elucidation of the tetracyclic 3-alklypiperidines. Chapter IV focuses on our synthetic strategy to access haliclonacyclamine C using carbon-carbon bond cross-coupling, alkene and alkyne macrocyclic ring-closing metathesis, and a stereoselective hydrogenation to introduce the four stereocenters incorporated within the core of these systems. Finally, Chapter V discusses the experimental details associated with the first total synthesis of haliclonacyclamine C.