Date of Award
Fall 12-2011
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.
Recommended Citation
Upadhyay, Sunil, "Synthesis and Antifungal Evaluation of Spirostane Saponins" (2011). University of New Orleans Theses and Dissertations. 1414.
https://scholarworks.uno.edu/td/1414
Rights
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