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Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis
Dissertation (MSc (Chemistry))--University of Pretoria, 2006.
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University of Pretoria
2013
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| _version_ | 1867613448071806976 |
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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 | © 2003 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc (Chemistry))--University of Pretoria, 2006. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/27820 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:36:18.085Z |
| 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:2263/27820 Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis Vleggaar, Robert upetd@up.ac.za Weldegebriel, Kibrom Asmerom Corncobs diseases and pests Fungal diseases of plants Spirochaeta Metabolites Diplodia maydis UCTD Dissertation (MSc (Chemistry))--University of Pretoria, 2006. The fungus Diplodia maydis, (synonym Stenocarpella maydis (Berk)) is worldwide one of the most important cob rot pathogens of maize. The isolation of stenocarpin, a metabolite toxic to ducklings, from maize cultures of D. maydis as the 4,6-0-diacetate derivative and its structure elucidation has been reported in the literature. Detailed NMR studies established the structure as either (3S,4R,6R,7R)- or (3R,4R,6R,7R)-spiro[(4,6, 7-trihydroxy-7-methyl-8-oxo-5,6,7,8-tetrahydroisochromane)-3 ,2' -tetrahydrofuran]. The absolute configuration of the C(3) spiroacetal stereogenic center remained unknown. The aim of the synthetic studies described in this dissertation was to develop a synthetic methodology for the spiroacetal moiety present in stenocarpin in order to establish unambiguously the C(3) absolute configuration. Retrosynthetic analysis of stenocarpin identified two model compounds (5S,lOR)- and (5R,lOR)-1,6-dioxaspiro[4.5]dec-8-en-10-o1 as the synthetic target. In turn the retrosynthetic analysis of these model compounds led to commercially available L-arabinose as starting material. Two strategies, which differ in the timing for the formation of the spiroacetal moiety as well as the initial type of protecting groups, were employed in the development of the synthetic route. In the first route the spirocyclisation reaction of a benzyl protected intermediate followed by the syn elimination of the cis-diol group resulted in the formation of only the (5S, lOR) model compound. The use of the acetonide and TBDPS protecting groups from the outset of the synthetic route and once again a spirocyclisation reaction, led to the formation of two spiro compounds epimeric at the C(5) spiro stereogenic centre, which could be separated and transformed by a syn elimination of the cis-diol group to the two model compounds. The configuration of the spiroacetal intermediates formed in the two synthetic routes and the changes in conformation that occurred in each of the steps were deduced from extensive NMR studies and especially the NOE technique. The results established the 3S configuration for stenocarpin and provided a viable synthesis for the (5S,lOR)-l,6-dioxaspiro[4.5]dec-8-en-1O-ol model compound that is to be used in the total synthesis of stenocarpin. In the dissertation the results of the first steps in a total synthesis, a study on the epoxidation of the double bond, is presented. Chemistry unrestricted 2013-09-07T12:26:20Z 2005-09-09 2013-09-07T12:26:20Z 2003-09-01 2006-09-09 2005-09-08 Dissertation Weldegebriel, KA 2003, Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/27820 > H897/ag http://hdl.handle.net/2263/27820 http://upetd.up.ac.za/thesis/available/etd-09082005-122736/ © 2003 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Corncobs diseases and pests Fungal diseases of plants Spirochaeta Metabolites Diplodia maydis UCTD Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title | Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title_full | Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title_fullStr | Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title_full_unstemmed | Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title_short | Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis |
| title_sort | synthetic studies on the spiroacetal moiety of stenocarpin a metabolite of diplodia maydis |
| topic | Corncobs diseases and pests Fungal diseases of plants Spirochaeta Metabolites Diplodia maydis UCTD |
| url | http://hdl.handle.net/2263/27820 http://upetd.up.ac.za/thesis/available/etd-09082005-122736/ |