Doctor of Philosophy (PhD) / This thesis describes synthetic studies towards the HIV-1 integrase inhibitory natural products lithospermic acid and integramycin, resulting in a formal total synthesis of the former. A modular, flexible and convergent synthetic strategy to lithospermic acid was devised. In this approach, a Sonogashira coupling was used to unite the C1–C7 and C20–C27 fragments that were subsequently manipulated to then participate in the key step of the synthesis, a palladium-mediated carbonylative annulation. Reduction of the benzofuran nucleus with magnesium in methanol then provided the desired dihydrobenzofuran core of lithospermic acid. Various protecting group strategies were investigated to complete this sequence in an efficient manner. Further synthetic manipulations afforded the complete C1–C9/C19–C27 fragment, which was united with the C10–C18 fragment to deliver the entire carbon skeleton of lithospermic acid. A two step deprotection sequence was undertaken, however, complications with the final deprotective step prevented definitive proof that the total synthesis of lithospermic acid had been achieved. An alternate protecting group strategy was sought, and a formal total synthesis of lithospermic acid was achieved by intercepting an advanced intermediate from a previous total synthesis. Several strategies for the enantioselective synthesis of the dihydrobenzofuran core of lithospermic acid were evaluated, however, none proved successful. A synthetic route towards the tetramic acid subunit of integramycin was also investigated. 3- Methoxymaleimide was constructed using known chemistry, and the regioselective reduction of this ring system was developed. Attempts to further functionalise this ring system were thwarted by difficulties associated with handling. The scope of the regioselective reduction was investigated on an array of N- substituted methoxymaleimides with the procedure found to be generally high yielding and highly regioselective.
| Identifer | oai:union.ndltd.org:ADTP/216259 |
| Date | January 2007 |
| Creators | Fischer, Joshua |
| Publisher | University of Sydney., School of Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | The author retains copyright of this thesis., http://www.library.usyd.edu.au/copyright.html |
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