Endeavors in Methodology Development and Natural Product Total Synthesis

This thesis deals with the development of new reaction methodology, as well as total synthesis of natural products.\ud Chapter 1 describes readily available rhodium(II) salts catalyzed B-H insertion reactions between NHC-boranes (NHC-BH3) and diazocarbonyl compounds (N2CR1COR2). Stable α-NHC-boryl carbonyl compounds (NHC-BH2-CHR1COR2) are isolated in good yields. The reaction is a reliable way to make boron-carbon bonds with good tolerance for variation in both the NHC-borane and diazocarbonyl components. It presumably occurs by insertion of a transient rhodium carbene into a boron-hydrogen bond of the NHC-borane. Competition experiments show that a typical NHC-borane is highly reactive toward rhodium carbenes.\ud Chapter 2 describes the synthetic routes towards the synthesis of tulearin A and tulearin C. Large scale synthesis of the bottom fragments (C1-C12) and the top fragment (C13-C26) for tulearin A was accomplished. Different synthetic routes were tested to accomplish the total synthesis of tulearin A. Some major problems toward the total synthesis of tulearin A were identified and solved. Meanwhile a novel synthetic route towards the total synthesis of tulearin C was developed. New methodologies were applied to make the synthesis more efficient. The total synthesis of tulearin C was not accomplished because of the difficulty of removal of the acetate protecting group at C17