University of Missouri - Saint Louis

The Graduate School

Announcement

An oral examination in defense of the dissertation for the degree

Doctor of Philosophy in Chemistry

Scott J. Hasty
M.S. in Chemistry, May 2010, University of Missouri-St. Louis
B.S. in Chemistry, May 2008, University of Missouri-St. Louis


New Methods and Strategies for Orthogonal Oligosaccharide Synthesis

 

Abstract

Although scientists have been able to isolate certain classes of naturally occurring carbohydrates (sugars), the overall availability of pure natural isolates remains low. As a result, chemical synthesis has been employed to access certain classes of complex carbohydrates. Unfortunately, traditional carbohydrate syntheses often require laborious protecting and/or leaving group manipulations that result in poor over-all yields. Additionally, controlling the stereoselectivity of coupling reactions between sugar units is a major obstacle for chemists. Hence, the development of efficient methods that would streamline the synthesis of complex carbohydrates in a highly stereocontrolled manner represents a timely and demanding area of research.
Presented herein is the investigation of S-benzimidazolyl (SBiz) glycosides as novel building blocks for oligosaccharide synthesis. Exploiting the tunable reactivity properties of the SBiz leaving group, we have been able to execute carbohydrate synthesis via very effective active-latent and orthogonal strategies. To gain a better stereocontrol during the coupling reactions, we investigated various silver salts as activators. This study led us to discover that the nature of counter anions may greatly affect the stereoselectivity of coupling reactions. Resultantly, we determined that silver perchlorate is the most beneficial activator for the synthesis of challenging α-linkages.


 

Date: June 28, 2013

Time: 10:00 a.m. to 12:00 p.m.

Place: 451 Benton Hall

 

Defense of Dissertation Committee

 

Prof. Alexei V. Demchenko, Ph.D. (Advisor)

Prof. Christopher D. Spilling, Ph.D.

 

Prof. James J. O’Brien, Ph.D.

Prof. Eike B. Bauer, Ph.D.