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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

New methods for 2-Deoxy-Beta-Oligosaccharide synthesis and progress towards the total synthesis of Lomaiviticinone

Pongdee, Rongson 30 September 2004 (has links)
The oligosaccharide domain of many secondary metabolites have been demonstrated to be pivotal for the biological efficacy of the parent glycoconjugate. In most cases, the alteration or removal of these carbohydrate residues results in the greatly diminished or completely abolished biological activity of the natural product. A common structural motif found in secondary metabolites possessing carbohydrate domains is the 2-deoxy-β-glycosidic linkage which are among the most difficult to establish in a stereocontrolled fashion. Chapter I provides background information describing the difficulties associated with the synthesis of 2-deoxy-β-glycosidic linkages in addition to a sampling of the current methodology available for their construction. Chapter II details our use of diethyl and pinacol phosphite glycosyl donors towards a direct synthesis of a designed 2-deoxy-β-oligosaccharide in a "one-pot" process which constitutes a novel approach towards the synthesis of these glycosidic linkages. Lomaiviticin A was isolated as the major metabolite from fermentation of the halophilic strain LL-37I366 which was later assigned the name Micromonospora lomaivitiensis. Lomaiviticin A displayed potent biological activity towards numerous cancer cell lines with IC50 values ranging from 0.01 to 98 ng/ml. While postulated to induce double-stranded DNA cleavage, the mechanism of action was unique when compared to known DNA-damaging agents such as adriamycin and mitomycin C. Chapter III details progress towards the synthesis of lomaiviticinone employing an "inside-out" strategy to take advantage of the molecule's own C2-symmetrical nature. The focus of the chapter will pertain to our efforts to construct the stereochemically-rich cyclohexenone central core highlighted by the use of organometallic C-C bond formation processes.

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