Doctor of Philosophy
Brian L. Pagenkopf
A second generation catalyst for the Mukaiyama oxidative cyclization for the formation of trans-THF rings is described. Co(nmp)2, displays increased stability to the reaction conditions, resulting in lower catalyst loadings, lower reaction temperatures, and significantly higher purity and yields of the products. Three procedures have been developed with this new water-soluble catalyst that greatly simplifies the post-reaction purification, making this procedure the premier method of forming trans-THF rings.
This new catalyst has been applied towards the total synthesis of the potently bioactive macrocycle, Amphidinolide C. Herein we report the successful synthesis of several fragments of the natural product, and our attempts at coupling them to complete the synthesis. The C(1)-C(9) was achieved via two routes, both utilizing the highly effective oxidation catalyst Co(nmp)2 to form the methyl substituted trans-THF ring. Synthetic highlights include a regioselective Shi epoxidation, and the design and introduction of a novel Lewis acid (BF2OBn×OEt2) to facilitate a stereoselective reductive epoxide opening. The C(18)-C(34) fragment was also achieved via two routes, culminating in both the shortest (11 steps) and highest yielding (26% overall yield) approaches to this segment. Synthetic highlights of this fragment include a selective methylation of a diyne, and a highly selective alkynylation of a THF aldehyde, achieving excellent dr (>20:1) without the addition of an external chiral compound. Advanced intermediates comprising the entirety of the carbon backbone of the molecule have been synthesized, which in theory could complete the total synthesis in as few as two bond forming steps.
Morra, Nicholas A., "Progress Towards the Total Synthesis of Amphidinolide C" (2012). Electronic Thesis and Dissertation Repository. 502.