Total Synthesis Of Nature Products Powered By Organocatlytic Reactions & Study Of Radical Reactions Promoted By Transition Metal

This dissertation consists of three parts: 1. The total synthesis of the new guaiane–type sesquiterpenoids, hedyosumins A/B/C; 2. The synthetic studies of platencin analogues; 3. Transition metal promoted or catalyzed radical reactions.Hedyosumins A-C are 8, 12-guaianolides isolated from Hedyosmum orientale. Our synthesis features the application of Harmata’s [4+3] cycloaddition reaction that efficiently generated the highly functionalized bicyclic core with a good enantioselectivity. Other key steps include an intramolecular aldol condensation reaction, an oxymercuration/demercuration enabled lactonization. The asymmetric reduction of enone catalyzed by(R)-CBS furnished allylic alcohol improving the enatiopurity of the product to an excellent level. The first catalytic enantioselective synthetic strategy for guaianolides was successfully developed that allowed the first and asymmetric total synthesis of hedyosuminsA, B, and C in 13 steps, 14 steps, and 13 steps, respectively. The synthetic route is quite efficient, with hedyosumins A, B, and C being obtained in 6.1%, 4.8%, and 6.2% overall yield, respectively.Platencin was discovered by Merck in 2007 as a potential antibacterial compound with novel structure. Based on the methodolodgy developed by our group, we constructed the bicycle-[2. 2. 2]-framework with organocatalytic conguate addition of β–carbonyl ester to nitroethylene. Then a radical reduction was developed to generate the methylene group from β–nitro bromide. Finally, we furnished the carbonyl group employing alkynyl addition followed by gold-catalyzed Meyer-Schuster rearrangement. After several redox manipulations and aldo cyclization, we completed the formal total synthesis of platencin. We also tried the addition of β-carbonyl ester to other β-nitroalkenes to construct some platencin analogues.Transition metal promoted radical reactions were described in the third chapter of this dissertation. Mn(OAc)3 promoted phosphonylation of α, β-unsaturated sulfones, Silver carbonate catalyzed direct Csp2-H phosphorylation of indoles in the presence of magnesium nitrate and the amination of arylhydrazines with amines under CoPc/Cu(OAc)2 relay-catalysis using air as sole oxidant to afford N-aryl amines were respectively introduced.