Studies On The Biomimetic Syntheses Of Callistrilones A-E

In this dissertation,the oxidative [3+2] cycloaddition reaction between isobutyrylphloroglucinol and ?-phellandrene is the key reaction to realize the biomimetic synthesis of natural product Callistrilones A-E.And the reaction types and reaction mechanism of oxidative cycloaddition involving phenol were studied.This paper is divided into two parts:Chapter I Biomimetic Syntheses of Natural Product Callistrilones A-EThe first triketone-phloroglucinol-monoterpene hybrids(Callistrilones A and B)were isolated from the plant Callistemon rigidus(Myrtaceae)in 2016 by Ye group.Callistrilones C,D,and E,which have a skeleton similar to that of callistrilone A,were isolated and synthesized by Ye Wencai and Li Chuangchuang's group in 2017.The novel skeleton and good antibacterial activity of these natural products have attracted our attention.According to the proposed biosynthetic pathway,there are two key reactions in the biosyntheses of these molecules: the formation of the dihydrobenzofuran ring by the [3+2] oxidative cycloaddition reaction of isobutyrylphloroglucinol with ?-phellandrene and Flavcsone selective reductive elimination to generate isobutylidenesyncarpic acid.Based on the previous research on biomimetic synthesis of isobutylidenesyncaric acid in our laboratory,we only need to solve the oxidative cycloaddition reaction between isobutyrylphloroglucinol and ?-phellandrene to construct the dihydrobenzofuran ring.Based on the biosynthetic pathway proposed in the isolated paper,we designed a bionic synthesis route.We used the known compound isobutyrylphloroglucinol(1-7a)as the starting material to construct the dihydrobenzofuran ring by the oxidative [3+2] cycloaddition reaction with ?-phellandrene(1-11).We have tried different oxidants such as CAN,Ag2 O,Ag OAc,Ag2CO3,Mn(OAc)3,Ph I(OAc)2,etc.To promote the oxidation [3+2] cycloaddition reaction between 1-7a and 1-11,We also screened for the reaction solvents and the amount of substrates used to obtain the key intermediates 1-24 and 1-26 in 24% and 50% yields,respectively.After several steps of transformation,the bionic syntheses of natural product callistrilones A-E was finally achieved.Through the synthesis of viminalin I and the optical rotation test we determined its absolute configuration.Chapter ? Research Progress of Oxidative Coupling Reaction of PhenolThe coupling reaction between phenol and different compounds can be used to construct the structural skeleton of various organic compounds.To date,many bioactive molecules containing dihydrobenzofuran(DHB)backbones have been reported,including a large number of natural products and synthetic compounds with useful biological activities.In this chapter,we mainly summarize the method of oxidative coupling of phenols with dicarbonyl compounds,benzoquinones,heterocyclic,olefins for the construction of dihydrobenzofuran backbones and other strategies for the construction of dihydrobenzofuran backbones...