Open Access Dissertation
Date of Award
This dissertation focuses on two different problems. The first part of this manuscript presents the application of a novel methodology to access the synthesis of oligosaccharide mimetics while the second part focuses on the study of the stereoelectronic effects of proximal C-O bonds in C- and O-glycosylation reactions.
The first chapter provides a brief overview of the important roles that oligosaccharides and glycoconjugates play in biological processes and sets out the major advances that have been made in the past few decades in the synthesis of such complex structures while bringing out the ongoing challenges and the limitations that impede the development of general methods with broad applicability.
In chapter two, the emphasis is placed on a new thioligation reaction developed in the Crich laboratory as a means for the chemical synthesis of linear mimetics of an important bacterial motif, the β-(1→6)-N-acetyl glucosamine polymer. Small, protecting group-free, pre-assembled sugar units are linked together into larger oligosaccharide chains by the desulfurative rearrangement of allylic disulfides.
The first part of chapter three presents the general mechanistic aspects of O-glycosylation reactions, before detailing them further in the context of glycosylation reactions using 4,6-O-benzylidene-protected donors. The second part covers underlying principles of protecting group reactivity and their affects on glycosylation reaction.
Chapter four looks into the stereoelectronic influence of the C3-O3 bond in 4,6-O-benzylidene protected gluco- and mannopyranoside donors. The stereoselective formation of C-glycosides in the 3-deoxy mannose and glucose series is compared to that in the more usual 3-OBn series. The results of this study provided complementary insights into the determining elements controlling the stereoselective formation of C-glycosides.
In chapter five, the influence of the 4,6-O-benzylidene group on reactivity is investigated in the galactose series by probing the disarming influence of the tg conformation of the C5-C6 bonds. Kinetic studies on 4,6-O-alkylidene galactoside derivatives and their carba-analogs revealed that, similarly to the glucose series, 4,6-O-acetals also exert a disarming effect on galactopyranosides reactivity.
This manuscript ends with an overall conclusion presented in chapter six. All compounds characterizations and data plots are presented in chapter seven, in the experimental section.
Moume-Pymbock, Myriame, "Synthesis Of Oligosaccharide Mimetics By The Desulfurative Rearrangement Of Allylic Disulfides And Stereoelectronic Influence Of C-O Bonds On C- And O-Glycosylation" (2012). Wayne State University Dissertations. 679.