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Synthetic Studies on the Lactosaminoglycan Models : Functionalization of Lactose as an Unused Disaccharide Resource

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Title: Synthetic Studies on the Lactosaminoglycan Models : Functionalization of Lactose as an Unused Disaccharide Resource
Other Titles: ラクトサミノグリカンの合成化学研究 : 未利用二糖資源としてのラクトースの機能化
Authors: Furuike, Tetsuya1 Browse this author
Authors(alt): 古池, 哲也1
Issue Date: 29-Sep-1995
Abstract: Oligosaccharide resources can be utilized as fine materials to construct further complicated and biologically important glycoconjugates. In addition to the known oligosacchride resources such as cellobiose, maltooligosacchrides, and N,N'-diacetylchitobiose, lactose which is obtainable from whey in large amount should be also highly functionalized and applied for glycoconjugate synthesis. Since this disaccharide contains a precusor of N-acetyllactosamine structure known as an important unit of complex carbohydrates, chemical conversion of lactose to further functional synthons for oligosacchride synthesis seems to be powerful and versatile strategy for glycosciences. The thesis is composed of six chapters. The first chapter describes general introduction to the significance of molecular recognition in nature based on the interaction of carbohydrates and proteins. In addition, an importance of cluster effects in sugar-protein interaction is described. In order to investigate the significance and mechanism of the cluster effects, we have to prepare some appropriately designed sugar-ligands. For this purpose, use of lactose as a key starting material might facilitate the synthetic procedure of new clustered model-ligands. In order to achieve more effective methodology to design "high density cluster ligands", it might be necessary to synthesize novel type of polymerizable sugar derivatives. Thus, in the second chapter of this thesis, a simple and efficient method for the syntheses of clustering-sugar homopolymers from ω-acryloylamimoalkyl glycosides of N-acetyl-β-D-glucosamine (GlcpNAc) as a simple model of sugar moiety was discussed in order to produce highly clustered glycoprotein models. Apparent association constants of wheat germ agglutinin (WGA) with a variety of clustered glycopolymers were determined and evaluated by measuring the change in fluorescence intensity produced by various concentrations of polymeric ligand. It was suggested that additon of the clustered glycopolymer to WGA induced much greater enhancement of the fluorescence intensity and a significant blue shift of the fluorescence emission maximum of WGA than did addition of the low-density glycopolymer derived from n-pentenyl type.In the third chapter, the syntheses of cluster-type homopolymers from ω-acryloylaminoalkyl glycosides of N-acetyllactosamine [β-D-Galp-(1→4)-β-D-GlcpNAc] derived from lactose were discussed in relation to the easy determination study of sugar-binding specificity of fluorescein isothiocyanated Erythrina Corallodendron lectin (FITC-ECorL). It was clearly demonstrated by using these polymers that fluorometric titration of FITC-ECorL with a variety of LacNAc polymers revealed an importance of the suitable spacing of the inter-sugar residues on the glycoprotein models for the efficient interaction with the binding sites of lectins Since multivalency of glycoprotein-sugar moiety has not been synthesized on the basis of macromolecular models, attention is next directed towards design of triantennary polymeric sugar ligands using acrylamide type aglycon. Thus, in the chapter 4, an efficient synthesis of a new glycoprotein model having clustered triantennary N-acetyllactosamine (LacNAc) using 4-nitro-4- [1-(3hydroxypropyl)]-1,7-heptandiol as a key starting material was examined. Using the Newkome's derivative, several model glycopolymers having different degrees of density of triantennary LacNAc residues were successfully prepared. Finally, in the chapter 5, for the easy and versatile chemical synthesis of oligosaccharide moieties of branching lactosaminoglycan model, new approaches of chemical modification of lactose were described. Use of 1,6-anhydro-β-lactose as a starting material was proved to establish synthetic strategy that permits the syntheses of a series of lactosaminoglycan models, since all hydroxyl groups of 1,6-anhydro-β-lactose can be distinguished by chemical modifications. Concluding remarks will be described in Chapter 6.
Conffering University: 北海道大学
Degree Report Number: 甲第3721号
Degree Level: 博士
Degree Discipline: 地球環境科学
Type: theses (doctoral)
Appears in Collections:学位論文 (Theses) > 博士 (地球環境科学)

Submitter: 古池 哲也

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