The synthesis of natural products has always been, and still is, of great interest for various reasons. Firstly, the molecular diversity of natural products pushes organic chemists to develop and apply new strategies and methods in organic synthesis. Secondly, the practice of natural product synthesis remains one of the best way to confirm the structure of a natural product. Meanwhile, it also provides a way for examining the true robustness of novel synthetic methods, which has to be highly selective and efficient to be applied in total synthesis. Thirdly, developing a total synthesis of a natural product, which is in most cases isolated with low yields and after intensive purifications, will in general allow to produce sufficient quantities for the study of its biological properties. Finally, chemists also have the opportunity to synthesize a series of analogs of a natural product by slight modifications of the synthetic route, these analogues enabling the study of structure/activity relationships and potentially possessing better pharmacological and physicochemical properties compared to the original natural product. In that context, this thesis work has focused on the total synthesis of two natural macrocyclic alkaloids by using copper catalysis in the key steps. In the case of synthesis of (-)-melanthioidine, a member of the dimeric macrocyclic diaryl ether tetrahydroisoquinoline alkaloid, copper catalysis was utilized in the key cyclodimerization step to form a diaryl ether bond bridged 20-membered ring constituted by two phenethyltetrahydroisoquinoline subunites. In this synthesis the configuration of the phenethyltetrahydroisoquinoline was controlled by a Bischler-Napieralski cyclization / Noyori asymmetric hydrogenation sequence starting from the corresponding amide, which could be readily prepared by a multi-step sequence from commercially available compounds. With the success we met in the synthesis of (-)-melanthioidine, we next turned our attention to the synthesis of paliurine F, which is a member of cyclopeptide alkaloids. In this synthesis, the copper-mediated cross coupling was implemented to install not only C(sp2)-O bond but also more challengingly to form C(sp2)-N bond to construct the 13-member ring of paliurine F in the regio-, chemo- and diastereo-selective manner, which eventually enabled us to develop a highly convergent approach to paliurine F.Finally, we also put our effort to the development of an efficient copper-mediated domino double Ullmann coupling-double Claisen rearrangement process starting from readily availble ene-diols and vinyl iodides. In this synthesis, the double Ullmann coupling product in situ underwent a single Claisen rearrangement followed by a microwave-assisted Claisen rearrangement to provide a highly functionalized 1,6-dicarbonyl compounds. In addition, our process was also shown to be successful for the functionalization of glycals. In conclusion, our work further highlight the efficiency of copper-mediated transformation in the synthesis of natural products and provide new strategies for the formation of symmetrial or, even more interestingly, non-symmetrical macrocyclic molecules. Moreover, combining copper-mediated reactions with pericyclic process such as Claisen rearrangement was also shown to be an efficient way for the development of novel synthetic methods. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
| Identifer | oai:union.ndltd.org:ulb.ac.be/oai:dipot.ulb.ac.be:2013/268602 |
| Date | 16 March 2018 |
| Creators | Wang, Jianjun |
| Contributors | Evano, Gwilherm, Moucheron, Cécile, Robiette, Raphael, Vincent, Stéphane, Jabin, Ivan |
| Publisher | Universite Libre de Bruxelles, Université libre de Bruxelles, Faculté des Sciences – Chimie, Bruxelles |
| Source Sets | Université libre de Bruxelles |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:ulb-repo/semantics/doctoralThesis, info:ulb-repo/semantics/openurl/vlink-dissertation |
| Format | 3 full-text file(s): application/pdf | application/pdf | application/pdf |
| Rights | 3 full-text file(s): info:eu-repo/semantics/openAccess | info:eu-repo/semantics/closedAccess | info:eu-repo/semantics/closedAccess |
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