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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Towards the synthesis of new macrocyclic receptors

Bukhari, Abeer January 2017 (has links)
Iron plays a fundamental role in the regulation of chemical processes within biological systems and the control of intracellular iron concentration has important consequences in the aetiology of a variety of disease states (e.g. neurodegenerative disorders). In this thesis, which is concerned with the identification of new macrocyclic receptors, the synthesis of (N,N',N''-((3S,7S,11S)-2,6,10-trioxo-1,5,9-trioxacyclododecane-3,7,11-triyl)tris(2,3-dihydroxybenzenesulfonamide), a mimic to the natural siderophore enterochelin, is reported. Two synthetic routes to the preparation of this macrocycle are presented where a sulfonamide residue is attached to a functionalised lactone core. The title compound was prepared either via the cyclotrimerzation of methyl N-((2,3-dimethoxyphenyl)sulfonyl)-L-serinate (“pre-functionalization” method) or by the elaboration of a preformed macrocyclic scaffold, (3S,7S,11S)-2,6,10-trioxo-1,5,9-trioxacyclododecane-3,7,11-triaminium chloride, with 2,3-dimethoxybenzenesulfonyl chloride (“post-functionalization” method). Late-stage demethylation of the macrocyle formed in these reactions - N,N’,N’’-((3S,7S,11S)-2,6,10-trioxo-1,5,9-trioxacyclododecane-3,7,11-triyl)tris(2,3-dimethoxybenzenesulfonamide) using BBr3 afforded the desired enterochelin analogue. These studies indicated that the “post-functionalisation” protocol afforded higher yields of the desired macrocycle in a process which was not marred by the concomitant formation of sulphonamide by-products. During the synthesis of 2,3-diacetoxy-5,6-dimethylsulfonyl chloride, a key intermediate for the assembly of functionalised sulphonamide siderophores, an ortho-quinone intermediate was found to undergo an intermolecular Diels-Alder reaction from which both the keto- ((1S*,4S*,4aR*,8aS*)-2,3,8,8a-tetramethyl-1,4,4a,8a-tetrahydro-1,4-ethanonaphthalene-5,6,9,10-tetraone) and enol- ((1S*,4R*,8aS*)-5-hydroxy-2,3,8,8a-tetramethyl-1,8a-dihydro-1,4-ethanonaphthalene-6,9,10(4H)-trione) tautomeric forms could be isolated and fully characterised by X-ray crystallography thereby constituting a rare example of desmotropy.

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