Sulfated carbohydrates play key roles in a wide range of biological processes such as blood clotting, viral entry into cells, amyloidogenesis, neurite outgrowth, tumor growth and metastasis. However, their synthesis still remains a considerable challenge. A general approach to the synthesis of sulfated carbohydrates was examined in which sulfate group is incorporated at the beginning of the syntheses as a protected sulfodiester. Towards this end, a series of sulfuryl imidazolium salts (SIS), a new class of sulfating agents, was prepared and examined as reagents for incorporating 2,2,2-trichloroethyl-protected sulfate esters into monosaccharides. The SIS that contained a 1,2-dimethylimidazolium moiety proved to be a superior sulfating agent compared to SIS bearing no alkyl groups or bulkier alkyl groups on the imidazolium ring. Difficult O- and N- sulfations that required prolonged reaction times and a large excess of the SIS bearing a 1-methylimidazolium group were achieved in high yield and in less time when employing less than half the 1,2-dimethylimidazolium derivative. Efforts were then made to apply the sulfate protecting group strategy to the total synthesis of a class of chondroitin sulfate glycosaminoglycans. These studies revealed some of the limitations of the sulfate protecting group approach to the synthesis of sulfated oligosaccharides. Studies on the selective introduction and isomerization of the carbobenzyloxy protecting group into 2,3-diols of 4,6-O-benzylidene galactose derivatives are also reported.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2008. / Titre provenant de l'écran titre. Bibliogr. p. 79-91.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 90-103). Also available in print.

Sulfated carbohydrates play key roles in a wide range of biological processes such as blood clotting, viral entry into cells, amyloidogenesis, neurite outgrowth, tumor growth and metastasis. However, their synthesis still remains a considerable challenge. A general approach to the synthesis of sulfated carbohydrates was examined in which sulfate group is incorporated at the beginning of the syntheses as a protected sulfodiester. Towards this end, a series of sulfuryl imidazolium salts (SIS), a new class of sulfating agents, was prepared and examined as reagents for incorporating 2,2,2-trichloroethyl-protected sulfate esters into monosaccharides. The SIS that contained a 1,2-dimethylimidazolium moiety proved to be a superior sulfating agent compared to SIS bearing no alkyl groups or bulkier alkyl groups on the imidazolium ring. Difficult O- and N- sulfations that required prolonged reaction times and a large excess of the SIS bearing a 1-methylimidazolium group were achieved in high yield and in less time when employing less than half the 1,2-dimethylimidazolium derivative. Efforts were then made to apply the sulfate protecting group strategy to the total synthesis of a class of chondroitin sulfate glycosaminoglycans. These studies revealed some of the limitations of the sulfate protecting group approach to the synthesis of sulfated oligosaccharides. Studies on the selective introduction and isomerization of the carbobenzyloxy protecting group into 2,3-diols of 4,6-O-benzylidene galactose derivatives are also reported.

No description available.

A general approach to the asymmetric syntheses of HETEs in both enantiomeric forms was developed. The syntheses of 8(S)-, 9(S)-, 11(S)- and 12(S)-HETE methyl esters, starting from D-arabinose, were accomplished. / A practical approach to the solution synthesis of fragments from Haemophilus influenzae type b capsular polymer was established, which opens a route to the development of a new vaccine against meningitis. The major aspects of this approach, stereocontrolled glycosidation, selective protection and deprotection, and efficient phosphorylation were detailed. The normal solution syntheses of the mono-, di- and tetrasaccharides were accomplished. / A new class of spacer for the linkage of the oligosaccharide with a protein was introduced. The spacer and the spacer-linked tetrasaccharide were prepared.

This thesis describes investigations into the use of electrochemical oxidation as a method for the activation of glycosyl donors, and in particular the application of this technique to the selective activation of one electrochemically active glycoside over another. The synthesis of twenty eight electrochemically active monosaccharide donors, including thio-, seleno- and O-glycosides with varying protecting group patterns and anomeric substituents is described, together with the synthesis of three electrochemically active monosaccharides with the potential to act as both glycosyl donors and glycosyl acceptors. The electrochemical analysis of these monosaccharides is reported and gives a detailed insight into the effect of various factors on the oxidation potentials of the monosaccharide donors and allows some general conclusions to be drawn. In addition the analysis of six monosaccharides by cyclic voltammetry at scan rates of up to 25 000 Vs^-1 allows their homogenous kinetics to be outrun and formal oxidation potentials obtained. Investigations into selective electrochemical glycosylations are reported, and the applicability of the analytical electrochemical studies to synthetic electrochemical reactions is demonstrated. Selective glycosylations are possible with selenoglycoside donors and either thio- or O-glycoside acceptors to give disaccharides. However the selective activation of selenoglycosides over thioglycosides is shown to be complicated by some underlying pathway for indiscriminate activation of both donor and acceptor. In contrast the use of an O-glycoside donor experiences no such problems. More detailed work on the underlying problems experienced with the thioglycoside acceptor was conducted, and the results are reported here. Investigations into electrochemical activation of the disaccharides are discussed, and the thioglycoside is shown to be easily activated to give a trisaccharide. At the time of writing this is believed to be the only electrochemically mediated trisaccharide synthesis reported in the literature. The O-glycoside however is shown to be inactive under the electrochemical oxidation conditions employed.

No description available.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 174-181).

Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Sept. 10, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Sciences, Agricultural, Food, and Nutritional Sciences, University of Alberta." Includes bibliographical references.