Date of Award

Fall 12-17-2011

Degree Type

Dissertation

Degree Name

Ph.D.

Degree Program

Chemistry

Department

Chemistry

Major Professor

Branko S. Jursic

Second Advisor

Mark L. Trudell

Third Advisor

Richard B. Cole

Fourth Advisor

Anantha Sankaranarayanan

Fifth Advisor

Lee Roy Morgan

Abstract

Methods for the preparation of novel antifungal saponins have been investigated in

order to further explore their medicinal utility and provide the opportunity to synthesize

their derivatives.

Through this work, several partially protected stereoisomers of Cholestane,

Androstane and Spirostane have been prepared which could be used for the synthesis of

various saponin derivatives in order to discover novel saponin based antifungal agent.

Various mono and disaccharide derivatives of these steroids have been synthesized and

evaluated for their antifungal activity against four pathogenic fungal strains. Among the

various derivatives maltose derivatives were found to have the best antifungal activity.

However there is a need for more extensive SAR studies to discover compounds with

better potency.

Additionally, the branched oligosaccharide synthesis was explored in two parts.

First, these results demonstrated that the central 2,3-branched portion can be synthesized

efficiently from a partially protected glucopyranosyl acceptor since the C-2 and C-3

alcohols differ in their reactivity in glycosylation reactions. Second, a tagged sugar based

strategy for synthesis of branched oliogosaccharides was developed, and found to be

effective for general synthesis of branched oligosaccharides.

Microwave assisted synthesis of cyclic imides have been explored this was a key

precursor for the synthesis of our tag molecules which were required for synthesis of

branched oligosachharides. A comparison of microwave versus conventional methods for

synthesis of cyclic imides has been studied. The synthesis of tagged sugars and their

selective deprotection to remove tag molecules were successfully explored in order to

have proof of concept for its applicability towards synthesis of branched

oligosaccharides.

Benzylic mono and dibromination was achieved in very high yields using

microwave conditions using environmentally friendly solvent in order to avoid use of

carcinogenic carbon tetrachloride as solvent for this type of reactions. In addition reaction

time was reduced to 30 minutes to 3 hours compared to convention methods, which

needed more than 15 hours for the benzylic bromination reaction.

Rights

The University of New Orleans and its agents retain the non-exclusive license to archive and make accessible this dissertation or thesis in whole or part in all forms of media, now or hereafter known. The author retains all other ownership rights to the copyright of the thesis or dissertation.

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