Date of Award
Doctor of Philosophy
Nicola L. Pohl
This dissertation focuses on two specific aspects of the chemistry of carbohydrates. The first is the solid- and fluorous-phase synthesis of oligosaccharides and their use in forming microarrays. The solid- and fluorous-phase synthesis of oligosaccharides has emerged as a powerful method for the development of improvements in terms of synthesis speed and efficiency. The advantage of solid phase synthesis can be obtained very high yields by use of excess donors, ease of purification, and synthesis automation. Moreover, there are still unsolvable matters in solid-phase synthesis of oligosaccharides, which have to use a way over excess of amount donor group in each reaction. The fluorou-phase synthesis has developed the new additional overcome method to synthesize oligosaccharide, which allow to use in the solution phase synthesis of oligosaccharides and to use equivalent donor group to the acceptor group. A new fluorous tag-assisted solution phase strategy allows the rapid, and potentially automated, modular synthesis of carbohydrates and their use in forming microarrays. A new simpler concept in microarray formation is based on noncovalent fluorous-based interactions. A fluorous tail is designed not only to aid in saccharide purification but also to allow direct formation of carbohydrate microarrays on fluorous-derivatized glass slides for biological screening with lectins, such as concanavalin A. The noncovalent interactions in the fluorous-based array are even strong enough to withstand the detergents used in assays with the Erythrina crystagalli lectin. Additionally, the utility of benzyl carbonate protecting groups on fucose building blocks for the formation of alpha-linkages is demonstrated;The second topic is the strategies for the chemoenzymatic synthesis of deoxysugar nucleotides and stable activated sugar mimics. The carbaglucose-1-phosphate and deoxyglucose-1-phosphate present evidence that these classes of enzymes can exercise kinetic discrimination in choosing carbohydrates of comparable binding affinity for catalytic turnover. Synthetic 6-deoxy, 4-deoxy, and 3-deoxyglucose-1-phosphate and the natural substrate glucose-1-phosphate were tested with a representative prokaryotic glucose-1-phosphate uridylyltransferase [EC 22.214.171.124] from Escherichia coli, which is also known to accept thymidine triphosphate, and the comparable eukaryotic enzyme from yeast. The results are reported the first synthesis of the carbocyclic version of the most common naturally occurring sugar-1-phosphate, glucose-1-phosphate, and its evaluation with bacterial and eukaryotic sugar nucleotidyltransferases. In contrast to results with the eukaryotic enzyme, the carbaglucose-1-phosphate serves as a substrate for the bacterial enzyme to provide the carbocyclic uridinediphosphoglucose. This result demonstrates the first chemoenzymatic strategy to this class of glycosyltransferase inhibitors.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Ko, Kwang-Seuk, "Solution, solid-phase, and fluorous-phase synthesis of carbohydrates and production of carbohydrate microarrays " (2006). Retrospective Theses and Dissertations. 1533.