SYNTHESIS OF UNIQUE BORACYCLIC SYSTEMS

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General aspects of proposed synthesis of Medium and Macrocyclic Compounds: An important challenge to synthetic chemists is the construction of medium and macrocyclic ring systems. Proposed in Part 1 of this application is our envisioned contribution using what is termed "Boron Template Synthesis". It is proposed to: (A) Assess the synthetic potential of forming bicyclic carboranes via hydroboration/carbonylation or equivalent process of heteroatom substituted triene substrates. (B) This boracycle will then be treated under conditions that effect fragmentation (Grob) to yield olefinic heterocycles containing a medium size ring (boron = heteroatom). Finally (C), the properties and synthetic utility, through replacement of Boron, of these boracycles will be investigated. Sesquiterpene (Pacifigorgo1) Total Synthesis: A Look at the Stereochemistry of Riveting. An important advantage in using the "Boron Template" synthetic strategy is the well documented and predictable chemo-, regio- and stereoselectivitiy of boron hydrides towards polyolefinic substrates. The overriding question which has generated this phase of our proposal deals with the stereochemistry of carbonylation (CO/cyanidation/carbanion insertion/etc.). To address this problem we propose the synthesis of pacifigorgo via Boron Annulation (stitching and riveting), the stereochemistry of the C-1 hydroxy1 group evolving from the riveting step. Based on the small amount of data available, we are predicting the formation of pacifigorgol from a boracyclane via carbonylation or equivalent process. We will explore the possibility that variations in riveting techniques might alter the stereochemical outcome of the boron replacement process. A major goal of this total synthesis is to present more insight into this carbon boron replacement process.