Studies Towards Asymmetric Total Synthesis Of Gymnothelignan N And Daphenylline

This thesis describes recent applications of benzene dearomatization strategy in the field of natural products synthesis and efforts towards asymmetric total synthesis of structurally novel natural products gymnothelignan N and daphenylline.The following three chapters are included:Chapter 1.Applications of benzene dearomatization strategy in natural products synthesis(Review).A brief introduction of the advantages of benzene dearomatization strategy for synthesis is given,thereafter,applications of this kind of strategy in natural products synthesis in recent years are selectively summarized by classification based on the reaction types of dearomatization.Finally,a personal viewpoint of the perspectives for the research of benzene dearomatization is provided.Chapter 2.Asymmetric total synthesis of gymnothelignan N.A brief introduction of the background for the isolation,bioactivity and synthesis of gymnothelinans and other related lignans is provided.And then we proposed a new plausible biosynthetic pathway for gynnothelignans,and accomplished an asymmetric bioinspired total synthesis of gymnothelignan N in 13 steps and 6.7%overall yield.The synthesis features an Evans syn aldol reaction,an intramolecular hydrogenative dehydration and a bioinspired strategic oxidative aromatization/Friedel-Crafts reaction.Furthermore,we established a 2,5-diaryltetrahydrofuran(DATHF)structure model and its general synthetic route,aiming for the foundation of a DATHF compound library to screen and discover bioactive chemical compounds for drug lead use.Chapter 3.Studies towards asymmetric total synthesis of daphenylline.A brief introduction of the background for the isolation of daphniphyllum alkaloids is given and recent synthetic progress of the calyciphylline-A type daphniphyllum alkaloids is also summarized.Thereafter,targeted to the structurally novel daphniphyllum alkaloid daphenylline,we developed an intramolecular[3+2]cycloaddition/N-alkylation cylization strategy and an intramolecular Diels-Alder cycloaddition/oxidative aromatization strategy for construction of its ABCE and DEF cyclic skeletons,respectively.On the basis of these strategies,we made some breakthroughs for asymmetric total synthesis of daphenylline.