Studies On Palladium-promoted Brook Rearrangement And Total Synthesis Of Isoabietenin A And Vincamajorines A

This thesis is mainly focused on the construction of vinyl cyclobutanols via palladium-promoted neutral 1,4-Brook rearrangement/intramolecular allylic cyclization cascade reaction,and the total synthesis of abietane diterpenoid isoabietenin A and monoterpenoid indole alkaloid vincamajorines A.It consists of the following four chapters: Chapter 1 Radical cascade reactions in total synthesis of natural products(review)This reviewer mainly introduces radical cascade reactions in total synthesis of natural products with novel framework.The radical cascade reactions are classified according to the center atom carrying the unpaired electron among the the attacking radical,such as carbon center radical,nitrogen center radical,other atom center rrradical,biradical.This reviewer also Chapter 2 Synthetic studies toward abietane diterpenoid isoabietenin AIn order to synthesize abietane diterpenoid isoabietenin A,radical cascade cyclization has been developed to efficiently construct the 6/6/5 fused tricyclic framework.Under mild reaction conditions,a tandem 5-exo-trig/6-endo-trig cyclization reaction processed smoothly using benzene halide as substrates.A series of oxa-and aza-tricyclic frameworks could be constructed via the radical cascade cyclization.Using this strategy,5-epi-7-deoxy-isoabietenin A was synthesized efficiently through a longest linear sequence of eleven steps from commercially available 3-isopropylphenol and ethyl 2-formylpropionate.Chapter 3 Palladium-promoted neutral 1,4-Brook rearrangement/intramolecular allylic cyclization cascade reaction: A strategy for the construction of vinyl cyclobutanolsPalladium-promoted 1,4-Brook rearrangement/intramolecular allylic cyclization cascade reaction was designed and developed.A series of strained vinyl cyclobutanol rings was constructed through activation of vinyl epoxides by palladium,1,4-Brook rearrangement,followed by regioselective and diastereoselective cyclization with a palladium complex of the resulting carbon anion.The method could also be applied to more complex substrate to afford the bridge [2.1.1] bicyclic skeleton.Neutral 1,4-Brook rearrangement was achieved under mild reaction conditions Chapter 4 Synthetic studies toward monoterpenoid indole alkaloid vincamajorines AFour precursors of the key α-furoylation was synthesized efficiently through reductive amination,Pictect-Splengler reaction and Dieckmann condensation from natural L-tryptophan as chiral sources.The transition-metal catalyzed α-furoylation of carboxide was systematic studied.The hexacyclic framework of vincamajorines A,monoterpenoid indole alkaloid containing a new C20 carbon skeleton,was constructed.