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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

Synthetic methodologies for the synthesis of 2,6-dideoxy glycosides

Jacobs, Buyiswa Getrude 13 June 2008 (has links)
The aim of this project was to develop a synthetic strategy for the production of uncommon sugars thevetose (6-deoxy-3-O-methylglucose) and cymarose (2,6-dideoxy-3-O-methylallose or 2,6-dideoxy-3-O-methylaltrose) derivatives, present in the trisaccharide moiety of a pregnane glycoside with appetite-suppressant activity. A D-thevetose glycosyl donor was prepared from methyl D-glucopyranoside. The first step of the synthesis was the formation of a 4,6-O-benzylidene derivative that was selectively methylated on the 3-hydroxy group by using a copper mediated alkylation process. Treatment with NBS and reductive removal of the resultant bromide produced the required protected thevetose glycoside. This success is a vast improvement compared to the published results of the patent reporting this synthesis. Attempts to prepare the 2α-iodo derivative by direct nucleophilic substitution of a 2-O-triflate manno-derivative resulted in a most unusual rearrangement reaction. Allal derivatives as starting materials in the preparation of 2α-iodo sugars were also unsuccessful due to steric hindrance provided by the axial 3-methoxy group. Preparation of a cymaroside precursor was achieved by using glucal as a starting material and by the inversion of C-3 in a consecutive oxidation/reduction sequence of the iodo acetate. Lastly, the preparation of the β-oleandroside derivative of cholesterol was achieved in a model reaction. The sugar oleandrose is a C-3 epimer to cymarose and it can be found in pregnane and cardenolide glycosides. / Professor F.R. van Heerden
2

Novel methodologies for the synthesis of C-aryl glycosides and progress toward the synthesis of the C-aryl glycoside natural products galtamycinone and kidamycin

Kaelin, David Earl 28 August 2008 (has links)
Not available / text
3

The use of glycoside uloses in asymmetric epoxidation.

January 2003 (has links)
by Yeung Kwan Wing. / Thesis submitted in: 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 68-73). / Abstracts in English and Chinese. / Contents --- p.i / Acknowledgement --- p.ii / Abstract --- p.iii / Abbreviation --- p.v / Chapter 1. --- Introduction --- p.1 / Chapter 1-1 --- Background --- p.1 / Chapter 1-2 --- Sharpless Epoxidation --- p.2 / Chapter 1-3 --- Mn-Salen Complexes for Epoxidation --- p.4 / Chapter 1-4 --- Oxaziridinium Salts --- p.6 / Chapter 1-5 --- Dioxiranes --- p.7 / Chapter 1-6 --- Asymmetric Epoxidation by Dioxirane --- p.11 / Chapter 2. --- Results and Discussion --- p.28 / Chapter 2-1 --- C-Glycoside Ulose Catalyst derived from L-arabinose --- p.28 / Chapter 2-2 --- Dioxirane epoxidation catalyzed by L-arabino-4-uloses --- p.30 / Chapter 3. --- Experimental Section --- p.51 / Chapter 4. --- References --- p.68 / Chapter 5. --- Appendix --- p.74

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