The syntheses of some naturally derived naphthoquinones

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dc.contributor.advisorGiles, Robin G Fen_ZA
dc.contributor.authorDe Koning, Charles Bernarden_ZA
dc.date.accessioned2016-09-28T19:09:04Z
dc.date.available2016-09-28T19:09:04Z
dc.date.issued1987en_ZA
dc.descriptionBibliography: pages 193-195.en_ZA
dc.description.abstractThe synthesis of the naphthalene core of the ansamycin antibiotics, 8-acetyl-3-acetylamino-5,7-dihydroxy-1,4-naphthoquinone from benzoquinone by means of simple reactions including, Diels-Alder adduct formation, mild acetylation, oxime formation and Beckmann rearrangement in five steps with an overall yield of 22% is described in Chapter 1. The synthesis of the naturally occurring naphthoquinone derivative, possessing anti tumour and antiprotozoal properties, bikaverin is described in Chapter 2. Starting from vanillin the key intermediate 2-(2'-benzyloxy-6'-methyl-4'-methoxybenzoyl)-1,4,5,6,8-pentamethoxynaphthalene was prepared in six simple steps in an overall yield of 18%. This key intermediate was converted into bikaverin utilizing two independent routes. In the first route the benzyl group was removed from the key intermediate by hydrogenolysis followed by oxidative spiro ring formation , with 2,3-dichloro-5,6-dicyanobenzoquinone. After effecting xanthone ring formation and removal of two methyl groups with lithium iodide, bikaverin was produced in six steps in an overall yield of 32%. In the second route the key intermediate was first oxidised by silver (II) oxide this was followed by removal of the benzyl group and two methyl groups peri- to the quinone with boron trichloride, which led to spontaneous spiro ring formation, ultimately bikaverin was produced in three steps in an overall of 34%. The syntheses of the naturally occurring product ventiloquinone E and its trans-isomer as well as an isomer of the naturally occurring ventiloquinone J and its trans-isomer are described in Chapter 3. Starting from 1,2,4,5,8-pentamethoxynaphthalene, the synthesis of which has been described in Chapter 2, ventiloquinone E was prepared in nine steps in an overall yield of 7%. Similarly an isomer of ventiloquinone J was also prepared from 1,2,4,5,8-pentamethoxynaphthalene in ten steps in an overall yield of 6%. In both cases a mixture of cis-and trans-isomers was obtained, a successful resolution of both mixtures was accomplished by thin layer chromatography. By two other methods the trans-isomer of ventiloquinone E could be prepared in either nine steps in an overall yield of 23% or in six steps with an overall yield of 30% starting from the same pentamethoxynaphthalene.en_ZA
dc.identifier.apacitationDe Koning, C. B. (1987). <i>The syntheses of some naturally derived naphthoquinones</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Chemistry. Retrieved from http://hdl.handle.net/11427/22000en_ZA
dc.identifier.chicagocitationDe Koning, Charles Bernard. <i>"The syntheses of some naturally derived naphthoquinones."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Chemistry, 1987. http://hdl.handle.net/11427/22000en_ZA
dc.identifier.citationDe Koning, C. 1987. The syntheses of some naturally derived naphthoquinones. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - De Koning, Charles Bernard AB - The synthesis of the naphthalene core of the ansamycin antibiotics, 8-acetyl-3-acetylamino-5,7-dihydroxy-1,4-naphthoquinone from benzoquinone by means of simple reactions including, Diels-Alder adduct formation, mild acetylation, oxime formation and Beckmann rearrangement in five steps with an overall yield of 22% is described in Chapter 1. The synthesis of the naturally occurring naphthoquinone derivative, possessing anti tumour and antiprotozoal properties, bikaverin is described in Chapter 2. Starting from vanillin the key intermediate 2-(2'-benzyloxy-6'-methyl-4'-methoxybenzoyl)-1,4,5,6,8-pentamethoxynaphthalene was prepared in six simple steps in an overall yield of 18%. This key intermediate was converted into bikaverin utilizing two independent routes. In the first route the benzyl group was removed from the key intermediate by hydrogenolysis followed by oxidative spiro ring formation , with 2,3-dichloro-5,6-dicyanobenzoquinone. After effecting xanthone ring formation and removal of two methyl groups with lithium iodide, bikaverin was produced in six steps in an overall yield of 32%. In the second route the key intermediate was first oxidised by silver (II) oxide this was followed by removal of the benzyl group and two methyl groups peri- to the quinone with boron trichloride, which led to spontaneous spiro ring formation, ultimately bikaverin was produced in three steps in an overall of 34%. The syntheses of the naturally occurring product ventiloquinone E and its trans-isomer as well as an isomer of the naturally occurring ventiloquinone J and its trans-isomer are described in Chapter 3. Starting from 1,2,4,5,8-pentamethoxynaphthalene, the synthesis of which has been described in Chapter 2, ventiloquinone E was prepared in nine steps in an overall yield of 7%. Similarly an isomer of ventiloquinone J was also prepared from 1,2,4,5,8-pentamethoxynaphthalene in ten steps in an overall yield of 6%. In both cases a mixture of cis-and trans-isomers was obtained, a successful resolution of both mixtures was accomplished by thin layer chromatography. By two other methods the trans-isomer of ventiloquinone E could be prepared in either nine steps in an overall yield of 23% or in six steps with an overall yield of 30% starting from the same pentamethoxynaphthalene. DA - 1987 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1987 T1 - The syntheses of some naturally derived naphthoquinones TI - The syntheses of some naturally derived naphthoquinones UR - http://hdl.handle.net/11427/22000 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22000
dc.identifier.vancouvercitationDe Koning CB. The syntheses of some naturally derived naphthoquinones. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Chemistry, 1987 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22000en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Chemistryen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherNaphthoquinoneen_ZA
dc.subject.otherRifomycinen_ZA
dc.titleThe syntheses of some naturally derived naphthoquinonesen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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