| This thesis is mainly divided into three parts, respectively involved in the syntheses of three kinds of natural products.Chapter 1:Total syntheses of Lachnone C and Gonytolide G.Many natural compounds which possess promising biological activities contain a structure of chromanone. Recently, scientists have isolated some chromanones with γ- lactone at its a-site. These compounds also have some biological activities, such as antibacterial, antifungal, anticoccidial and cytotoxic activities.We firstly synthesized two chromone compounds 1-6 and 1-6’through the Baker-Venkatarama n rearrangement, then Lachnone C and Gonytolide G were synthesized, using TMSI catalyzed conjugate addition reaction as key steps, with the yield of 8.2% and 9.5%, respectively. This work has a significant guidance for the synthesis of Xanthone-ant hraquinone heterodimers natural compounds.Chapter 2:The studies on the synthesis of Xanthone-anthraquinone heterodim mers.Xanthone-anthraquinone heterodimers are a series of fungal metabolites with unique structure of ethylene-bridge-bicyclo skeletons and promising biological acti vities, such as antibacterial, antifungal, anticoccidial, antiplasmodial and cytotoxic activities. Towards the synthesis of Xanthoquinodin A3, We ftrstly designed two model moleculars 2-1 and 2-1’based on the analysis of structure of Xanthoquinodin A3. Considering the generated sequence of the seven-membered ring and the double bond, we designed two routes for the syntheses of these two model compounds.In the first route, we planted to introduce the double bond firstly, then constructed the seven-membered ring through Buchwald coupling reaction and radical reaction. Unfortunatedly, the substrate 2-9 is aromatization under the coupling conditions, and changed to the compound 2-9’. We hence modified the route and designed a new model compound 2-12 through further analysis. We planed to use compounds 2-5 and 2-12 to form compound 2-2, then the seven-membered ring can be formed through the free radical reaction. This plan is still in progress.In the second route, we planted to construct the seven-membered ring firstly, then introduced the double bond by Aldol or D-A reaction. We firstly used compoun ds 2-5 and 2-13-8 to form 2-15, then planed to adopt intramolecular radical reaction or electrophilic substitution reaction to synthesize compound 2-16. Finally, we planted to make use of the compound 2-16 to synthesize the model molecular 2-1. The route is under way.Chapter 3:The studies on the synthesis of seven-membered unsaturated lacton e.The seven-membered unsaturated lactone derivatives are one of the most common compounds in nature. They have clinical functions such as antibacterial, cell toxicity and immune inhibitory activities. Because of its easily preparation, the seven-membered unsaturated lactone derivative is an effective component in the synthesis of hydroxyl or carbonyl lactone derivatives within the polycyclic structure. As a result, we herein have designed a special kind of seven-membered unsaturated lactone compound, we planed to finish its synthesis and test its biological activity.We synthesized the compounds 3-11 firstly, then tried a series of conditions for RCM reaction to build the seven-membered lactone structure, however, in all conditions tested, we got the intermolecular product 3-12’. We also added the bulk lewis acid to promote the intramolecular reaction, however, we still did not obtained the target intramolecular cyclization product. We then designed a second route through further analysis of the structure of the moleculer. We planed to synthesize compound 3-20 firstly, then through borohydrogenation, oxidation, methylation and epoxidation, opened the expoy, and at last, closed the ring to form the seven-membe red lactone. Finally, the target molecular could be synthesized through the rout provided by figure 3-13. |
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