UC Berkeley

The first section of this dissertation describes our efforts to further develop the rhodium–catalyzed 1,2–addition of pinacolboronic ester nucleophiles into unactivated ketones. This reaction represents a mild and efficient alternative for performing this carbon–carbon forming transformation, which traditionally employs harsh conditions, and is especially useful in the context of total synthesis. Our observation that bisphosphine ligands are a beneficial additive in this transformation led to its elaboration into an asymmetric reaction manifold. The second section of this dissertation centers on the use of a key hydrindanone intermediate as a valuable synthetic precursor to the diterpenoid alkaloids and the phragmalin–type limonoids. Chapter 2 begins with a discussion of the isolation and classification of the diterpenoid alkaloids. In addition, major synthetic contributions made by others toward the synthesis of these natural products are also discussed. Our own synthetic approach to these compounds is then detailed, including the construction of the versatile denudatine type core. Central to the success of this strategy was a highly diastereoselective Diels–Alder cycloaddition to furnish a functionalized hydrindanone, the stereochemical information of which was relayed throughout the rest of the synthesis. Chapter 3 focuses on the phragmalin–type limonoids. Previous landmark syntheses of limonoid natural products are first summarized following a brief overview of their isolation and classification. Our strategy for accessing the bridging framework of these natural products is then disclosed. Key to the success of this approach was the concept of network analysis allowing for disconnection of the bridging framework into a fused [6,5] system, thus simplifying its construction.