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Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology
Dissertation (MSc (Chemistry))--University of Pretoria, 2007.
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University of Pretoria
2013
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| _version_ | 1867613520106881024 |
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| access_status_str | Open Access |
| author2 | Vleggaar, Robert |
| author_browse | Vleggaar, Robert |
| author_facet | Vleggaar, Robert |
| collection | Thesis |
| dc_rights_str_mv | © University of Pretor |
| description | Dissertation (MSc (Chemistry))--University of Pretoria, 2007. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/27113 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:37:27.084Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/27113 Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology Vleggaar, Robert happy.maringa@sappi.com Msibi, Happy Hazel Biochemistry Fusarium moniliforme Plants Disease Fumonisins UCTD Dissertation (MSc (Chemistry))--University of Pretoria, 2007. Fusarium verticillioides (=Fusarium moniliforme) a common fungal contaminant of maize throughout the world has been associated with diseases in both man and animals. The structure of the fumonisins, a family of structurally related mycotoxins isolated from cultures associated with the high incidence of human oesophageal cancer in the Transkei region in South Africa and with equine leucoencephalomalacia, a neurological disorder in horses and donkeys, has been established. The main mycotoxin, fumonisin B₁ consists of the diester formed by the C(14) and C(15) hydroxy groups of (2S,3S,5R,10R,12S,14S,15R,16R)-2-amino-12,16-dimethyleicosane-3,10,14,15-pentaol with the Si carboxy group of propane-1,2,3-tricarboxylic acid. A comparison of the structures of the 28 known fumonisins isolated since 1988 reveals that they share a common structural motif for the C(11)–C(20) unit, and probably also the same stereochemistry for the 4 stereogenic centres present in this part of the C20 backbone. Disconnection of the C(9)–C(10) bond in a retrosynthetic analysis of the fumonisins identifies (3S,5S,6R,7R)-3,7-dimethylundecane-1,5,6-triol as a common building block for the synthesis of any of the fumonisins. In the dissertation the retrosynhetic analysis of this 3,7-dimethylundecane-1,5,6-triol building block identifies a simple precursor, ethyl 2-heptenoate, as the starting material for the proposed synthetic route toward this target. The Sharpless asymmetric epoxidation reaction plays a pivotal role in this synthetic route as all 4 stereogenic centres present in the 3,7-dimethylundecane-1,5,6-triol target are generated by this methodology at three different stages of the proposed synthesis. The epoxy alcohol formed at each stage was subjected to regioselective ring opening followed by a protective group strategy which allowed for the protection of the secondary hydroxyl group as the benzyl ether and left the primary hydroxyl group, available after oxidation to the aldehyde, for a two-carbon chain extension to an α,β-unsaturated ester. This ester in turn was reduced to an allylic alcohol which formed the starting material for a second cycle of reactions. In this manner a synthetic route towards the target compound was developed and problems associated with the route investigated. The dissertation shows that a viable route was developed with complete stereochemical control in the formation of the stereogenic centres, even though the final product, the protected 3,7-dimethylundecane-1,5,6-triol was not obtained due to time constraints and material shortages. Chemistry MSc unrestricted 2013-09-07T10:38:17Z 2007-08-16 2013-09-07T10:38:17Z 2007-04-24 2007-08-16 2007-08-10 Dissertation Msibi, HH 2007, Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/27113> Pretoria http://hdl.handle.net/2263/27113 http://upetd.up.ac.za/thesis/available/etd-08102007-135031/ © University of Pretor application/pdf University of Pretoria |
| spellingShingle | Biochemistry Fusarium moniliforme Plants Disease Fumonisins UCTD Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title | Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title_full | Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title_fullStr | Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title_full_unstemmed | Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title_short | Studies toward the stereoselective synthesis of the C(10)-C(20) unit of the fumonisins using Sharpless methodology |
| title_sort | studies toward the stereoselective synthesis of the c 10 c 20 unit of the fumonisins using sharpless methodology |
| topic | Biochemistry Fusarium moniliforme Plants Disease Fumonisins UCTD |
| url | http://hdl.handle.net/2263/27113 http://upetd.up.ac.za/thesis/available/etd-08102007-135031/ |