Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651371
Title: Oxidation and evaluation of calcium-complexing properties of certain oligosaccharides : synthesis of model compounds for glucose-based polysaccharides
Author: Gebbie, Stuart J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
Abstract:
The improved synthesis of two methyl glycosides, viz methyl 4-O-methyl-α-D-glucopyranoside and methyl 4-O-(α-D-glucopyranosyl)-α-D-glucopyranoside (methyl α-maltoside) from readily available starting materials is described for use as model compounds for oxidative studies of the industrially important polysaccharide amylose. Attempts to acetylate methyl-α-D-glucoside regioselectivity proved fruitless, whilst regioselective pivaloylation was more successful, albeit in yields of poor synthetic utility. In a variation to this approach, the glucoside, is synthesized via selective tri-O-benzoylation of methyl-α-D-glucoside with the regiospecificity of the reaction being a function of the relative strengths of intramolecular hydrogen bound rings, which are governed by the conditions under which the reaction is performed. In the second step, methylation of the free hydroxy group can only be achieved under pressure with silver oxide as catalyst. The target compound is obtained in the final step by conventional cleavage of the ester functions. Initial attempts to synthesise methyl-α-maltoside were convergent, being conducted with variants of the Koenigs-Knorr methodology and using reactions of previously prepared haloglucosides with variously protected 4-hydroxymethyl-α-D-glucosides. No combination of catalysts could be found to activate either of the substrates, or in an alternative strategy, mediate the reaction between a halomaltoside and an alkoxy nucleophile. The target maltoside is formed eventually via the selective anomeric deprotection of per-O-acetylated maltose, followed by stereospecific methylation in a manner similar to that described previously. It is found that in this penultimate step an intramolecular silver alkoxy - esteric salt inhibits mutarotation, thus allowing the predominant formation of the α-anomer. Further deacetylation gives rise to methyl-α-maltoside in 63% yield and in only three steps.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.651371  DOI: Not available
Share: