Studies On Cycloisomerizations Of Enynes And Total Synthesis Of Cladosporin And Isoclaosporin

This thesis is mainly focused on the construction of natural product-oriented skeletons by exploring novel reactions. In which, cycloisomerization of enynes and the total synthesis of natural products cladosporin and isocladosporin were involved. The main content is divided into the following sections:Part1. Cycloisomerization of enynes:challenging metal-catalyzed rearrangements and the application in total synthesis of natural or biologically active products.(Review)Among the extraordinary variety of metal-catalyzed reactions, enyne rearrangements are growing in importance as-depending on the functional groups and the experimental conditions-several transformations are possible which lead to cyclic derivatives. Such metal-catalyzed processes are inherently atom economical and result in a significant increase in structural complexity. In general, they are operationally simple, safe, and convenient to perform even on a large scale. This review will attempt to emphasize historical and major contributions to the field and will focus on the applications in total synthesis of natural or biologically active products.Part2. Cycloisomerization of enynes:propargylic estersAs part of the wide interest in enyne cycloisomerization, a specific class of alkynes is being studied extensively:propargylic esters. The first using of metal-involved1,3-dipolar synthon, which might experience cycloaddition with an appropriate olefin to generate cycloaddition product, was explored. In addition, the cycloisomerization of arylpropargylic esters for the construction of indanone skeleton was also tested.Part3. Asymmetric total synthesis of cladosporin and isocladosporinThe first asymmetric total synthesis of cladosporin and isocladosporin from commercial available (S)-propylene oxide and (S)-epichlorohydrin as chiral sources, respectively, was accomplished. The strategy was developed based on a notion of concise enantioselective assembly of the tetrahydropyran ring. The relative configuration of isocladosporin was defined through this total synthesis.