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Title: Synthesis and evaluation of novel carbohydrate-based chiral auxiliaries
Author: McDougall, Douglas
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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The work described in this thesis is primarily concerned with a series of asymmetric transformation reactions employing a newly developed (-)-D-fructose derived 1,3-oxazin-2-one (77) as a chiral derivatising agent. The synthetic route utilised the well-known but little used stereospecific nitrene insertion process. The ability of the auxiliary to successfully participate in these reactions ranged from excellent, as was the case in aldol reactions, to disappointingly poor when failing to react at all, as was the case in alkylation reactions. The auxiliary was also utilised in Lewis-acid catalysed Diels-Alder cycloaddition reactions in which contrasting results were achieved. For α-bromination of the N-propionyl derivative, almost total asymmetric stereocontrol was obtained, whereas the performance of the auxiliary in asymmetric conjugate addition reactions of the corresponding N-acrylate compounds, once again produced mixed results. When employed in acylation reactions, Manders reagent (methylcyanoformate) was required to promote the return of the desired product. The competence of 77 as a resolving agent was highly favourable in the resolution of a racemic primary amine as well as a racemic acid halide. In summation, the overall performance of this auxiliary was very promising. Although the reactions conducted have on occasion exposed ambiguous reactivity, any weaknesses present are now well-defined and most can be avoided or overcome. Adequate diastereofacial differentiation is usually achieved and product separation is effected routinely and non-destructively by mild hydrolysis. Furthermore, a high incidence of crystallinity is found in products and intermediates which greatly facilitates product separation and identification. Towards the end of the thesis a further auxiliary (147) derived from isosorbide is described. The synthesis of this 1,3-oxazolidin-2-one based auxiliary required selective protection procedures which resulted in an overall workable yield.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available