Synthetic Studies Towards (+)-Dactylol Utilizing an Oxonium Ylide Rearrangement and Related Studies.

Abstract

Dactylol is a structurally interesting sesquiterpene natural product. One of its key structural features is an the eight-membered ring. The challenges of synthesizing an eight membered ring are discussed in Chapter 1. In addition, various methods for generating an eight-membered ring are highlighted within the several discussed total syntheses of dactylol. The West group has developed methodologies for generating eight membered rings that have utilized the rearrangement of an oxonium ylide. This method has been applied towards the total synthesis of dactylol. In Chapter 2, the previous synthetic routes as well as extensions to these routes are discussed. In addition, an advanced route towards the natural product has been developed and is examined in detail. In our approach towards the total synthesis of dactylol, we discovered a side product during a dicyclohexylcarbodiimide esterification reaction. This side product was determined to be an imino-oxazinone. The synthesis of these heterocycles has been developed using an in situ generated acyl ketene, which undergoes a formal [4+2] cycloaddition with a carbodiimide. This convergent approach has been applied to several different acyl ketenes and carbodiimides and is discussed in Chapter 3. 4 During our studies of dactylol we became interested in the Stevens rearrangement of an oxonium ylide with an adjacent cyclopropylcarbinyl group. This rearrangement substrate has not been previously investigated and is interesting as it would give valuable mechanistic information on the Stevens rearrangement. The preliminary investigations into these compounds are discussed in Chapter 4.