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Title: Synthesis and investigation of hydrazinolysis of some N-substituted dehydroalanine derivatives
Author: Süzen, S.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1997
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Chapter 1 provides a general introduction to the release of the oligosaccharide residues of glycoproteins by alkaline, enzymatic, and especially hydrazinolysis reaction. Problems in the release of O-linked oligosaccharides from glycoproteins, the importance of hydrazinolysis conditions, and degradation during the hydrazinolysis are discussed. The possible reaction mechanism of the hydrazinolysis of O-linked oligosaccharides, which involves a β-elimination reaction resulting in a dehydroalanine moiety (from L-serine) than can then react with hydrazine, is discussed. Chapter 2 describes the synthesis of the model compounds, N-substituted dehydroalanine derivatives, which were chosen to study the behaviour towards hydrazine of the alkene that results from β-elimination. Difficulties with the preparation of N-benzoyl derivatives led to the use of N-benzyloxycarbonyl as an alternative N-protecting group. However N-benzyloxycarbonyl was found to be affected by hydrazine, and attention was concentrated on other N-acyl protected dehydroalanine derivatives. Dehydroalanine amides proved to be more difficult to synthesise than dehydroalanine esters, and the simplest route to amide derivatives involved the coupling of N-acetyldehydroalanine (2-acetamidopropenoic acid) with amines. Chapter 3 introduces the hydrazinolysis results and discussion of the model compounds which were treated with anhydrous hydrazine under different conditions. Small scale reactions were conveniently monitored by NMR. This initial step was shown to be conjugate addition of hydrazine to the alkene. This was followed, in the case of ester derivatives, by cyclisation to form pyrazolidinone derivatives, but such cyclisation was not observed for amide derivatives. The conjugate addition product was the major product of the hydrazinolysis of N-acetyldehydroalanine amides. This result did not support the hypothesis that incomplete release of oligosaccharides from mucus glycoproteins resulted from pyrazolidinone formation, which would generate N-terminal glycosylated serine (or threonine) residues that were more resistant to β-elimination.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available