Total Synthesis Of Daphnilongeranin A And Paxiphylline E And Catioic Cyclization To Construct The Tricyclic Hetero-Containing Motif Of Hapalindole-like Molecules

The description in this dissertation is divided into two parts:the total synthesis of the Daphniphyllum alkaloids daphnilongeranin A and paxiphylline E and using catioic cyclization to construct the tricyclic hetero-containing motif of hapalindole-type natural products.Daphniphyllum alkaloids are natural products with a complex cage-like skeleton,more than three hundred of which have been isolated and reported and most of which possess such significant physiological activity and medicinal value that they have attracted the considerable attention of chemists.After a long time and intensive research,our group has completed the ingenious total synthesis of several Daphniphyllum alkaloids and been able to prepare key intermediates on a large scale.On this basis,this dissertation describes our total synthesis of daphnilongeranin A and paxiphylline E.Tetracyclic enedione was used as a key intermediate to construct quaternary carbon-containing multifunctionalized five-membered ring in one step exploiting Trost[3+2]reaction.Key six-membered heterocycle was built up by acid catalyzed elimination of allylic alcohols.Then Vilsmeier reaction and Corey-Gilman-Ganem oxidation introduced C-15 carbomethoxy and through ajusting oxidation state,daphnilongeranin A and paxiphylline E were synthesized.The hapalindole-type natural products contain a wide range of biological activities,which have attracted immense interest from isolation chemists,pharmacologists and synthetic chemists who had completed a lot of significant research since their isolation was reported.Although hapalindole-type natural products own potential drug-like properties,their specific mechanism of effect is indistinct yet.In spite of the structural variability of hapalindole-type natural products,the basic motif is the indole tricyclic scaffold which our group constructed utilizing mimetic oxidative Prins-cyclization strategy and synthesized several hapalindole-type natural products.On this basis,cationic cyclization to synthesize indole tricyclic motif was studied in this dissertation and the introduction of heteroatoms on its aliphatic ring was expected to change the basicity and liposolubility of the compounds.Besides,hetero atom is able to suffer from diverse conversions to provide more compounds which can be tremendously helpful in the field of drug research.