<p> Sialic acids are acidic monosaccharides with 9-carbon backbone that are found at the outermost of the mammalian cell membrane. They are a family of about 50 naturally derivatives of neuraminic acid, with N-acetyl neuraminic acid being the most common member. Its biological importance, as a terminal component of glycoconjugates, ranges from cell-cell interactions to pathogens attacks. Thus, the stereoselective synthesis of sialic acid-containing glycoconjugates with high yields is very important but unfortunately also a synthetic challenge in the carbohydrate synthesis field.</p><p> Regardless tremendous advancement in the field, sialic acid glycosylations (sialylations) are still a limiting factor in the synthesis of complex carbohydrates, which are biologically relevant for the design of therapeutics.</p><p> Based on the recent finding by De Meo <i>et. al.</i> on the existence of a conformational equilibrium at the oxacarbenium ion level that suggested positions C-4 and C-7 might be relevant in sialylation reactions; and on the recent reports by Demchenko et. al. on Hydrogen-bond-mediated aglycone delivery (HAD), we report herein the introduction of Picoloyl at C-4 and C-7 on thiosialyl donors. We also report the testing of the corresponding sialyl donors in several sialylation reactions, to elucidate the hypothesis of a Hydrogen-bond-mediated aglycone delivery (HAD) mechanism. However, exceptionally high stereoselectivities, yields and decreased reaction times were observed in the presence of an excess of triflic acid as a co-promoter.</p><p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:10615600 |
| Date | 01 November 2017 |
| Creators | Escopy, Samira |
| Publisher | Southern Illinois University at Edwardsville |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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