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|Title:||Part I, Aromatic annelation : synthesis of naphthalenes ; Part II, C-glycosyl anthraquinone synthesis : total synthesis of vineomycinone B2 methyl ester|
G-glycosyl anthraquinone synthesis
|Authors:||Gomez Galeno, Jorge E.|
|Keywords:||Naphthalene -- Synthesis|
Hydroxyanthraquinone -- Synthesis
|Abstract:||Part One: A synthesis of naphthalenes by an aromatic annelation sequence is described. α-unsubstituted ketones were converted into naphthalenes in three steps: (1) conversion Into the corresponding α-hydroxymethylene followed by O-silylation. (2) addition of benzyl magnesium chloride followed by dehydration to afford an unsubstituted enal and (3) acid catalyzed cyclizatlon to generate the naphthalene. Several naphthalenes were prepared by this sequence, and the potential of the sequence is illustrated by the synthesis of a phenanthrene. Part Two: The synthesis of functionalized hydroxyanthraquinones is reported. The method utilized was applied to a total synthesis of vineomycinone B2 methyl ester, the aglycone of the C-glycosyl anthraquinone antibiotic vineomycin B2. Hydroxyanthraquinones were protected as the corresponding methoxymethyl ethers and reduced to the anthracenes with sodium borohydride in refluxing isopropanol. These anthracenes could be cleanly lithiated and functionalized by reaction with reactive electrophiles. The lithio derivatives could also be captured by stannylation and the stannanes iodinated. These iodoanthracenes underwent Pd-catalyzed coupling reactions to generate the corresponding C-C bonds in a highly regiospecific manner. The use of a protected glucal derivative generated from the commercially available tri-O-acetyl-D-glucal afforded a C-glycosyl anthracene. Hydrogenation with sodium cyanoborohydride in methanolic HCl generated the corresponding β-C-glycosyl anthracene. Further stannylation of this C-glycoside afforded a stannane that was coupled with a chiral dioxinone to incorporate the alkyl side chain. Addition of lithium dimethylcuprate results in a functionalized anthracene that contains all of the carbon - carbon bonds present in vineomycinone 82 methyl ester, and all the asymmetric centers in the correct configuration. Elaboration into vineomycinone 82 methyl ester took place by oxidation to the corresponding 9,10-anthraquinone followed by removal of all protecting groups with methanolic HCl.|
Thesis (Ph. D.)--University of Hawaii at Manoa, 1990.
Includes bibliographical references.
xi, 98 leaves, bound ill. 29 cm
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|Appears in Collections:||Ph.D. - Chemistry|
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