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The synthesis of derivatives of naturally occurring naphthalenes
Includes bibliographical references.
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| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Department of Chemistry
2016
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| _version_ | 1867613316292018176 |
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| access_status_str | Open Access |
| author | Knight, Lorraine Shirley |
| author2 | Giles, Robin G F |
| author_browse | Giles, Robin G F Knight, Lorraine Shirley |
| author_facet | Giles, Robin G F Knight, Lorraine Shirley |
| author_sort | Knight, Lorraine Shirley |
| collection | Thesis |
| description | Includes bibliographical references. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/17082 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:10.861Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Chemistry |
| publisherStr | Department of Chemistry |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/17082 The synthesis of derivatives of naturally occurring naphthalenes Knight, Lorraine Shirley Giles, Robin G F Chemistry Naphthalene Rifomycin Includes bibliographical references. The ansamycins are a large group of natural products which have attracted considerable attention, largely as a result of their range of biological activity. The laboratory synthesis of an ansamycin has been simplified into the independent construction of the aromatic nucleus and the ansa chain, followed by their combination to form the macrocyle. The project described in Chapter 1 was designed to devise a novel, convenient, and efficient synthesis of a substituted 1,4-naphthoquinone which would function as a model for the naphthoquinonoid nucleus of the rifamycin subclass of these antibiotics. In this synthesis, 1,4-benzoquinone was converted into 8- acetyl-5,7-dihydroxy-6-methyl-3-propionylamino-1,4-naphthoquinone in six steps in an overall yield of 20%. The key step in this reaction sequence was the introduction of the C-6 methyl group via a regioselective lithiation/methylation reaction. Compounds which can be structurally defined as bioreductive alkylating agents have considerable potential as antineoplastic agents, according to H.W. Moore (Science, 1977). The protoaphins possess certain structural features which suggest their capability to function as such alkylating agents. Reductive cleavage of the aphid pigment, protoaphin-fb has been shown to give quinone A together with glucoside B, while protoaphin-sl on similar treatment affords quinone A', epimeric with quinone A at C-4, together with the same glucoside B. Professor Giles and co-workers have synthesised the 7,9-dideoxyquinone derivatives of both quinone A and A', as well as quinone A and A' themselves. The second chapter in this thesis describes three different approaches to the synthesis of a 4,10-dihydroxy-7,9-dimethoxy- 1,3-dimethyl-1H-naphtho[2,3-c]pyran analogous to glucoside B. The first two routes describe the construction of a naphtho[ 2,3-c]pyran of the correct relative stereochemistry using the novel reactions pioneered in this Department during the synthesis of 7,9-dideoxyquinone A. In the first method, the pyran ring was constructed with a C-5 oxygen substituent which was subsequently removed. The second method however, differs substantially from this route in that the C-5 substituent was not present during ring closure, hence eliminating the need to remove it at a later stage. The key step in the third approach involved the isomerisation of a dioxolane substituted naphthalene by an intramolecular version of the Mukaiyama reaction. Treatment of a C-8 brominated dioxolanyl naphthalene with titanium tetrachloride resulted in the formation of two angular naphtho[l,2-c]pyrans with the same relative stereochemistry of the pyran ring. An interesting bromine migration occurred after isomerisation had taken place. However, it is suggested that decreasing the size of the C-4 protecting group on the naphthalene nucleus prior to isomerisation, may allow the formation of the linear naphthopyran. 2016-02-17T07:16:24Z 2016-02-17T07:16:24Z 1988 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/17082 eng application/pdf Department of Chemistry Faculty of Science University of Cape Town |
| spellingShingle | Chemistry Naphthalene Rifomycin Knight, Lorraine Shirley The synthesis of derivatives of naturally occurring naphthalenes |
| thesis_degree_str | Doctoral |
| title | The synthesis of derivatives of naturally occurring naphthalenes |
| title_full | The synthesis of derivatives of naturally occurring naphthalenes |
| title_fullStr | The synthesis of derivatives of naturally occurring naphthalenes |
| title_full_unstemmed | The synthesis of derivatives of naturally occurring naphthalenes |
| title_short | The synthesis of derivatives of naturally occurring naphthalenes |
| title_sort | synthesis of derivatives of naturally occurring naphthalenes |
| topic | Chemistry Naphthalene Rifomycin |
| url | http://hdl.handle.net/11427/17082 |
| work_keys_str_mv | AT knightlorraineshirley thesynthesisofderivativesofnaturallyoccurringnaphthalenes AT knightlorraineshirley synthesisofderivativesofnaturallyoccurringnaphthalenes |