The syntheses of some naturally derived naphthoquinones

 

Show simple item record

dc.contributor.advisor Giles, Robin G F en_ZA
dc.contributor.author De Koning, Charles Bernard en_ZA
dc.date.accessioned 2016-09-28T19:09:04Z
dc.date.available 2016-09-28T19:09:04Z
dc.date.issued 1987 en_ZA
dc.identifier.citation De Koning, C. 1987. The syntheses of some naturally derived naphthoquinones. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/22000
dc.description Bibliography: pages 193-195. en_ZA
dc.description.abstract 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. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Naphthoquinone en_ZA
dc.subject.other Rifomycin en_ZA
dc.title The syntheses of some naturally derived naphthoquinones en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Chemistry en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation De 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/11427/22000 en_ZA
dc.identifier.chicagocitation De 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/11427/22000 en_ZA
dc.identifier.vancouvercitation De 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/11427/22000 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


Files in this item

This item appears in the following Collection(s)

Show simple item record