Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

Acinetobacter baumannii is a gram-negative bacterium species that is responsible for nosocomial infections. It has shown antibiotic resistance and has been designated an urgent threat by the CDC. In Chapter 1, I highlight my efforts in the synthesis of a Kdo building block in the journey towards the construction of an A. baumannii lipooligosaccharide (LOS) core pentasaccharide- a potential candidate for glycoconjugate vaccine against A. baumannii infection. I talk about various optimizations and improvements in the Kdo monosaccharide synthesis and the mechanistic insights I provided about a critical transformation in the synthetic sequence.

Chemical O-glycosylation is a significant research area in carbohydrate chemistry as it focuses on the installation of the O-glycosidic linkage. O-glycosylation reactions give rise to 1,2-cis and 1,2-trans diastereomers. The synthesis of 1,2-trans diastereomers is relatively facile as compared to their 1,2-cis counterparts. In Chapter 2, I talk about my attempts towards photochemical epimerization of a 1,2-trans sugar moiety into its 1,2-cis diastereomer.

Chapter 3 details the study to test the authenticity of the ‘Ether Model’ in explaining the 1,2-cis selectivity of the O-glycosylation reactions conducted in ether solvents. The ‘Ether Model’ has been widely cited in carbohydrate chemistry to explain the 1,2-cis selectivity in certain O-glycosylation reactions. The literature is replete with examples of 1,2-cis-selective O-glycosylation reactions that employ ether solvents and activators/promoters furnishing triflate or perchlorate counteranions. This latter fact appears to be largely overlooked, and there is strong evidence that these counteranions play a non-innocent role in O-glycosylation reactions.

Date

5-10-2024

Committee Chair

Ragains, Justin R.

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Available for download on Saturday, May 10, 2025

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