Studies Towards Synthetic Chemistry Oriented Carbon-carbon Bonds Formation And Its Application To Natural Products Synthesis

The construction of carbon-carbon bonds is the core problems of current organic synthesis,Diels-Alder reaction and C-H bond activation reaction are the most widely used methods for building carbon-carbon bonds.A large number of important bioactive natural products have been isolated from the natural plant resources,this thesis covers the efficient total syntheses of Diels-Alder natural products and rutaecarpine alkaloids,which both exhibit significant promising antioxidant activity.Approximately 40 different kinds of structurally unique prenylflavonoid DielsAlder natural products have been isolated from various Moraceous plants,structurally,these molecules all possess at least one 2'-hydroxychalcone moiety as well as polyphenol structures.Diels-Alder reaction is likely one of the most powerful reactions for the construction of complex polycyclic structures,but most Lewis acid is not able to catalyze the cyclization reaction of 2'-hydroxychalcone as the dienophile,so the enantioselective synthesis of this family of natural products remains elusive to date.We select 2'-hydroxylchalcone and isoprene as model substrates to investigate the asymmetric Diels-Alder reaction,the chiral VANOL-boron Lewis acid complex could afford the corresponding Diels-Alder adducts in satisfying yield and enantioselectivity.Based on our ability to achieve the enantioselective synthesis of(-)-nicolaioidesin C and(-)-panduratin A,we also applied the asymmetric method in the model reaction of calyxin Y,and more structurally complex Diels-Alder natural products sanggenon C and D,which exhibit importmant biological activities.Rutaecarpine was the main composition of nearly ripe fruit of Evodia rutaecarpa,which could efficiently activate the Nrf2-Keap1 signaling pathway,indicated that it maybe serve as a potential antioxidant drug.This thesis made a study on palladium catalyzed intramolecular oxidative cross-coupling reaction,rutaecarpine and 7,8-dehydrorutaecarpine can be synthesized via palladium-catalyzed oxidative double cross-coupling.Through the screening of oxidative cross-coupling conditions,it is believed that the Pd(OAc)2 /Cu(OAc)2.H2 O /pyridine catalyst system is useful for the synthesis of quinazolinecarbolin alkaloids.Rutaecarpine and 7,8-dehydrorutaecarpine were synthesized in one-pot,this strategy constitutes a potentially novel synthetic approach for the synthesis toward quinazolinecarbolin alkaloids.The preliminary study on biological mechanisms in the Nrf2-Keap1 pathways were investigated.