Application Of Asymmetric PEDA Reaction In Nature Products Synthesis

Photo promoted excited state organic chemical reaction is an important reaction type of synthetic chemistry,it allows for the formation of a high degree of molecular complexity in one step.This thesis focuses on the asymmetric photoenolization DielsAlder reaction（PEDA reaction）under UV-light and its application in natural products synthesis.Part one: Total synthesis of aglacins A,B and E via intermolecular asymmetric PEDA reaction.Aglacins belong to aryltetralin cyclic ether lignans.An asymmetric photoenolization/Diels–Alder（PEDA）reaction,between electron-rich 2-methylbenzaldehydes and unsaturated lactones,was developed to directly construct the basic tricyclic core of aryltetralin lactone lignans with high enantioselectivity.Base on intermolecular asymmetric PEDA reaction,brominated hydrolysis was used to introduce the oxidation state of benzyl position.The coupling reaction catalyzed by Pd（0）connected the aromatic ring fragments.After simple transformation,the first asymmetric total synthesis of aglacins A,B and E was achieved by 13 14 steps,the absolute configuration of these natural lignans was revised.This strategy was also used to efficiently prepare naturally occurring aryl–dihydronaphthalene-type lignans（–）-7,8-dihydroisojusticidine B and（+）-linoxepin,as well as 27 members of natural product-like molecules bearing an allcarbon quaternary center at C-8’.Finally,we also conducted a preliminary biological activity study.Part one: Study on diastereoselectivity and enantioselectivity of intramolecular PEDA reaction and the total synthesis of abietane diterpene.With respect to the intramolecular PEDA reaction,the rule of Ti（Oi-Pr）4 as Lewis acid in this reaction was studied.The reactivity and diastereoselectivity useing large steric hindrance substrate was solved.After the screening of chiral TADDOL-type ligands and adjustment of the relationship between substrate structure and reactivity,the intramolecular asymmetric PEDA reaction was achieved with excellent enantioselectivity.The basic core of tricyclic diterpenes containing quaternary carbons at the benzylic position was rapidly constructed through intramolecular asymmetric PEDA reaction.Studies on the synthesis of abietane diterpenes were carried out,the basic core of Coleon diterpenoids was constructed.