Synthesis and Antifungal Evaluation of Spirostane Saponins

<p> <p>Methods for the preparation of novel antifungal saponins have been investigated in</p> <p>order to further explore their medicinal utility and provide the opportunity to synthesize</p> <p>their derivatives.</p> <p>Through this work, several partially protected stereoisomers of Cholestane,</p> <p>Androstane and Spirostane have been prepared which could be used for the synthesis of</p> <p>various saponin derivatives in order to discover novel saponin based antifungal agent.</p> <p>Various mono and disaccharide derivatives of these steroids have been synthesized and</p> <p>evaluated for their antifungal activity against four pathogenic fungal strains. Among the</p> <p>various derivatives maltose derivatives were found to have the best antifungal activity.</p> <p>However there is a need for more extensive SAR studies to discover compounds with</p> <p>better potency.</p> <p>Additionally, the branched oligosaccharide synthesis was explored in two parts.</p> <p>First, these results demonstrated that the central 2,3-branched portion can be synthesized</p> <p>efficiently from a partially protected glucopyranosyl acceptor since the C-2 and C-3</p> <p>alcohols differ in their reactivity in glycosylation reactions. Second, a tagged sugar based</p> <p>strategy for synthesis of branched oliogosaccharides was developed, and found to be</p> <p>effective for general synthesis of branched oligosaccharides.</p> <p>Microwave assisted synthesis of cyclic imides have been explored this was a key</p> <p>precursor for the synthesis of our tag molecules which were required for synthesis of</p> <p>branched oligosachharides. A comparison of microwave versus conventional methods for</p> <p>synthesis of cyclic imides has been studied. The synthesis of tagged sugars and their</p> <p>selective deprotection to remove tag molecules were successfully explored in order to</p> <p>have proof of concept for its applicability towards synthesis of branched</p> <p>oligosaccharides.</p> <p>Benzylic mono and dibromination was achieved in very high yields using</p> <p>microwave conditions using environmentally friendly solvent in order to avoid use of</p> <p>carcinogenic carbon tetrachloride as solvent for this type of reactions. In addition reaction</p> <p>time was reduced to 30 minutes to 3 hours compared to convention methods, which</p> <p>needed more than 15 hours for the benzylic bromination reaction.</p> </p>

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2011

Author dc:creator

• Upadhyay, Sunil

Contributors dc:contributor

• Branko S. Jursic
• Mark L. Trudell
• Richard B. Cole

• Saponins, Oligosaccharide, Stereoisomer, Aglycone, Cholestane, Androstane,
• Chemistry

Repository record dc:identifier

https://scholarworks.uno.edu/td/1414

OAI identifier oai:identifier

oai:scholarworks.uno.edu:td-2418