Motanine Intermediate Synthesis And Nazarov Cyclization Reaction Research

Montanine,is an alkaloid isolated from Rhodophiala bifida bulb with potential anti-arthritic activity.Regarding the chemical synthesis of montanine-typealkaloids,great effort has been made over the past twodecades.Despite the substantial progress made in theracemic and asymmetric synthesis of themontanine-type alkaloids,a general strategy for the effectivebioinspired total synthesis of these architecturally uniquemolecules has not previously been explored.The Nazarov Cyclization is a rare example of a Lewis acid-catalyzed 4-π conrotatory electrocyclic reaction.Asymmetric induction could be achieved if a chiral Lewis acid were able to control the direction of the conrotatory closure.However,only a few such reactions have been reported.Common drawbacks are low enantioselectivity and the use of nearly stoichiometric amounts of the chiral Lewis acids,which must still be overcome.This thesis mainly consists of the following parts:Chapter 1,the recent advances in the Nazarov cyclization reaction were reviewed,especially the application of transition metal catalysis.Chapter 2,the synthesis methods of key intermediates of montanine were studied.The racemic synthesis of key intermediates was carried out using ketal as raw materials through reductive amination,oxidation,acylation and other reactions.At the same time,starting from pentenoic acid,Occurs on ozonation,chiral tert-butyl sulfinamide was introduced as a chiral amino group,than unsaturated alkenone was obtained by olefin metathesis reaction.Chapter 3,the cyclization reaction of Nazarov reaction was studied.A series of reaction conditions were tested to improve the stereoselectivity,but no obviously efficacy to be found.