Cation-induced Semipinacol Rearrangement And Synthetic Application

Daphniphyllum alkaloids are a massive class of nature products with multifarious polycyclic structure and copious chiral carbon atoms.There have been no less than 320 members of this sort of alkaloids isolated and identified up till the present moment.Calyciphylline A-type alkaloids,a subclass of Daphniphyllum alkaloids with their unique “dome-like” framework along with complex carbocyclic structure and jammed vicinal quaternary carbon centers,are quite difficult to synthesize.Ang Li?s group and Hong-bin Zhai?s group published the total synthesis of the Calyciphylline A-type alkaloids.Before that,however,just some works toward construction of the complex poly-carbocyclic frameworks had been completed.The semipinacol rearrangement induced by carbon-containing electrophile can install the spirocyclic structure and contigeous quaternary carbon centers,and the side carbon-chain introduced can further be transformed for synthetic purpose.So this efficient method has plenty of possibilities in the synthesis of nature molecules with spirocyclic ring systems and quaternary carbon centers.But this promising method faces some challenges,such as the low-activity and steric hindrance of substrates and electrophiles.This work is based on previous research of the synthesis of Daphniyunnine B with the Nicholas/semipinacol rearrangement cascade reaction.And we tried two ways to fulfill the total synthesis from the former substrates.This thesis consists of two main parts.Part I summarizes the structures of Daphniphyllum type alkaloids,indicating the specific structural features of Calyciphylline A-type alkaloids.A detailed conclusion of their synthetic efforts has been made.Part II mainly discusses our synthesis work.According to the difference between the strategies,this part is divided into two sections: a)efforts to fulfil the synthesis of Daphniyunnine B based on the 3-rings substrate,b)efforts to work out the synthesis of Daphniyunnine C through the Pauson-khand reaction.