Synthetic Studies Of Alkaloid Mersinine A

This thesis mainly focused on synthetic studies of Mersinine A involving a rhodium-catalyzed cascade reaction.It consists of the following two parts:Chapter 1.A overview of Mersinine A and the related backgroundMersinine A,a monoterpenoid indole alkaloid,was initially isolated by Kam group in 2001 from the leaf extract of Kopsia singapurensis.This family of natural product possess novel pentacyclic skeleton containing five contiguous stereogenic centers,two of which are quarternary carbons.This chapter briefly describes the intramolecular 1,3-dipolar cycloaddition reactions of carbonyl ylides and their applications in synthesis of the aspidosperma alkaloids.In addition,the synthetic applications of α-imino metal carbenes derived from the N-sulfonyl-1,2,3-triazole were also described.Based on these synthetic advances,a rhodium-catalyzed intramolecular [3+2] dipolar cycloaddition reaction was proposed for the synthesis of Mersinine A.Chapter 2 and Chapter 3.Synthetic studies of Mersinine AWe focused on the synthetic studies of Mersinine A through two synthetic routes.The first synthetic route is initially to combine the alkene fragment with multi-substituted piperidone motif by acylation reaction,which is then intend to link to the aryl moiety via Suzuki coupling reaction and underwent a rhodium-catalyzed intramolecular [3+2] dipolar cycloaddition reaction to construct core tricyclic skeleton of Mersinine A,however the Suzuki coupling reaction failed after several attempts.The second synthetic route is to connect the aryl and alkenyl segments together by Suzuki coupling reaction,and then to achieve the final connection with the multi-substituted piperidone fragment via acylation reaction.Finally,we obtained the desired product which jointed with the three requisite fragments successfully.An initial investigation of rhodium-catalyzed intramolecular [3+2] dipolar cycloaddition reaction has also been made.