Studies on total syntheses of jujuyane, fluvirosaones A, B, secu'amamine A, and conidiogenones

Abstract

The diverse and complex structures of organic natural products and their biological activities have brought a lot of effort to synthesize them. In particular, it is a long interest of synthetic chemists to efficiently introduce several structural elements such as 8-membered carbocycles, aza-cycles, and triquinanes found in compounds with strong biological activity. This dissertation describes the synthetic studies toward three different types of natural products with those structural elements. Novel synthetic strategies were developed based on the structural analysis of organic molecules and the consideration of the biosynthetic pathways of natural products, and through this, the each natural product could be successfully accessed. In each synthesis, characteristic cycloadditive transformations were devised to provide effective access to the polycyclic compounds with multiple stereogenic centers. In chapter 1, the total synthesis of (±)-jujuyane, a densely functionalized cyclooctanoid natural product, is described. This synthesis was the first application of (5+3)-dimerization reaction of oxidopyrylium ylide that forms the cyclooctanoid core structure along with inherited stereochemical bias.In chapter 2, a biomimetic total syntheses of fluvirosaones A, B and secu’amamine, utilizing a novel skeletal rearrangement in Securinega skeleton which have immediate biosynthetic significance, are presented.In chapter 3, studies toward the divergent total syntheses of cyclopiane diterpenoids featuring a unique 6/5/5/5-fused tetracyclic framework is detailed. TMM cycloaddition controlled by steric and electronic effects of substituents enabled rapid access to the cyclopiane tetracyclic structure, and formal total synthesis of conidiogenone B and diversity oriented synthetic strategy for various cyclopiane diterpenoids were explored based on this finding.