Total Synthesis Of Ergot Alkaloid Aurantioclavine And Lycopodium Alkaloid Phlegine A

This dissertation focuses mainly on total syntheses of ergot alkaloid aurantioclavine and new Lycopodium alkaloid phlegine A. We accomplished the concise efficient catalytic asymmetric total synthesis of ergot alkaloid aurantioclavine and the precursors of tetracyclic skeleton of Lycopodium alkaloid phlegine A.This dissertation consisted of the following parts:In part one, the overview of four asymmetric total synthesis of aurantioclavine and four total synthesis of communesin F is presented.In part two, enantioselective synthesis of (-)- and (+)-aurantioclavine are accomplished based on the key step of transition metal iridium-catalyzed N-allylation amination. The total synthesis, only 8 steps and 30% overall yield is the shortest route for catalytic asymmetric synthesis ergot aurantioclavine. The synthetic procedure features a lithiation-formylation reaction, an Ir-catalyzed intramolecularly asymmetric amination and Julia-Kocienski reaction. The protocol for generating the system of chiral center with N-heteroatom via an Ir-catalyzed intramolecularly asymmetric amination of secondary allylic alcohol 5 in the presence of Carreira ligand is first exploited in the synthesis of natural products. This strategy is expected to be further extended to other alkaloid synthesis.The total synthesis of Lycopodium alkaloid phlegine A has been investigated in the third part. Phlegine A has synthetic challenging owing to the novel 5/6/6/6 tetracyclic skeleton with 5 chiral centers and vicinal two quaternary centersIn this chapter, we have explored the total synthesis of phlegine A in two routes. In the first route, a key tricyclic intermediate was synthesized in 9 steps which featured a Helquist annulation. In the second route, we tried more concise DA reaction route for key step. We synthesized a key bicyclic intermediate which was confirmed via X-ray single crystal analysis and developed several precursors of DA reactions and tried the key DA reactions.