Synthetic Studies And Total Synthesis Of Indole-Type Alkaloids

The thesis aims at the studies on the synthesis of a few naturally occurring indole-type alkaloids. It maily consists of the following two parts:Part I: Synthetic studies on the efficient construction of the basic skeleton of double-indole type alkaloids.In the exploration to the synthesis of the basic skeleton of double-indole type alkaloids, we successfully constructed the hexahydroindole nucleus using the Br~+ promoted intramolecular cyclization/elimination developed in our group. Based on this basic skeleton, the key Br~+ promoted semipinacol rearrangement was then investigated. Despite, we did not obtain the desired basic skeleton of double-indole nucleus, but the experiment results of this part encouraged us to explore the total synthesis of signle-indole type alakoids and has become the foundation of the second work.Part II: Synthetic studies and total synthesis of signle-indole type alakoids. 1. A general and efficient approach to both 7-aryloctahydroindole and cis-3a-aryloctahydroindole alkaloids has been developed. The key step involves Michael additions of the corresponding kinetics and thermo-dynamics lithium enolates of ketone to the versatile building blocks: nitroethylene. Two representa-tive members: (±)-y-Lycorane and (i)-Crinane, have been synthesized in 28% and 36% overall yields respectively. Meanwhile, it is worthy to note that, as the powerful acceptor of the strategy-key Michael addition reaction, nitroethylene is firstly introduced in the construction of Amaryllidaceae type alkaloids and it represents the shortest route to this kind of alkaloids. 2. A general and efficient approach to both aromatic andnon-aromatic-type Erythrinan and Homoerythrinan alkaloids has been developed. The two-step sequence, alkylation of ketone with various N-substituted iodoacetamide followed by a N-acyliminium ion promoted intramolecur cyclization, represents the shortest route to Erythrinan and Homoerythrinan derivatives. Two representative members, (±)-3-demethoxyerythratidinone and (rfc)-Erysotramidine, have been synthesized respectively.