Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.666209
Title: Application of nitrile oxide-isoxazoline chemistry for the synthesis of higher monosaccharides and azasugars
Author: McGhie, Karen E.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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Abstract:
Nitrile oxide-isoxazoline chemistry has been utilised in a convergent approach towards the synthesis of a series of undecose monosaccharides. The sequence involves three stages. The cycloaddition of a five-carbon nitrile oxide to a hex-5-enofuranose derivative provides an eleven carbon framework incorporating a 2-isoxazoline. Reductive hydrolytic cleavage of the heterocycle to a β-hydroxyketone followed by reduction affords the target 6-deoxy-higher sugar. Two ω-unsaturated monosaccharide derivatives, 3-O-benzyl-5,6-dideoxy-1,2,O-isopropylidene-α-D-xylo-hex-5-enofuranose and methyl 5,6-dideoxy-2,3-O-isopropylidene-α-D-lyxo-hex-5-enofuranoside, were selected for this purpose. 2,3:4,5-Di-O-isopropylidene-D- and L-arabinononitrile oxides were generated from the corresponding oximes by a chlorination-dehydrochlorination protocol. Cycloaddition to both alkenes proceeded with good π-facial selectivity (64-78% de). In each instance the major adduct possessed the R-configuration at the new asymmetric centre (C-5), corresponding to an erythro relationship between it and the adjacent C-4 position of the attached furanose unit. The observed selectivities are rationalised in terms of the 'inside alkoxy effect' and the 'homoallylic' modification proposed by Houk and De Micheli. In contrast, the configuration of the carbon adjacent to the nitrile oxide was found to have negligible effect on the observed erythro: threo ratios. Reductive hydrolytic cleavage of the 2-isoxazolines provided the required β-hydroxyketones, accompanied by formation of a diastereoisomeric mixture of γ-amino alcohols. Subsequent reduction of the carbonyl of the former afforded the corresponding 1,3-diols, which were convertd to their ketals in order to aid in structure determination. Finally isopropylidene deprotection and peracetylation provided the corresponding 6-deoxy-octa-acetyl undecofuranoses.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.666209  DOI: Not available
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