Studies Toward The Total Synthesis Of Alsmaphorazine D And Melicolone B

This dissertation focuses on:(1)Total synthesis of alsmaphorazine D.(2)Synthtic study towards melicolone B.The first part is the total synthesis of alsmaphorazine D.Alstonia plants,abundant species in the tropical regions of Africa and Asia,are well-known as a rich source of unique heterocyclic alkaloids containing a monoterpene indole skeleton.These alkaloids have attracted great attention in the biogenetic and biological fields for their anticancer,antibacterial,anti-inflammatory,antitussive,and antimalarial properties.A concise total synthesis of rac-alsmaphorazine D has been described for the first time.This efficient synthetic strategy features four key transformations:1)a catalytic intramolecular oxidative cyclization for the ?-lactamindole backbone;2)an oxidative cyclic aminal formation for the hexahydropyrrolo[2,3-b]pyrrole framework;3)a radical cyclization in the formation of diazabicyclo[3.3.1]nonane structure;and 4)a one-pot desilylation/double epimerization reaction that affirms the relative stereochemistry.The second part are the synthetic studies of melicolone B.We proposed our first generation synthtic route,which was base on biomimetic synthesis.Ring contraction reaction was implemented through Wolff rearrangement,and obtained the Prins reaction precursor,unfortunately,biomimetic synthesis strategy did not achieve the core construction of three-membered ring skeleton.The three-membered ring structure was constructed by titanocene-mediated radical cyclization in the second generation synthtic route,subsequent research is still ongoing.