Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697250
Title: Approaches towards the synthesis of gem-difluorinated monosaccharide analogues
Author: Pintat, Stéphane
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2003
Availability of Full Text:
Access from EThOS:
Access from Institution:
Abstract:
This thesis describes the synthesis of gem-difluorinated cyclic molecules using building block approaches based mainly on ring-closing metathesis (RCM) using commercially available ruthenium catalysts such as Grubbs' catalyst. In the first instance, 1-bromo-1,1-difluoroprop-2-ene was used to synthesise difluorinated dihydropyrans in order to demonstrate that the unprecedented RCM of a substrate containing two fluorine atoms in the allylic position could be achieved. A similar approach allowed the highly diastereoselective synthesis of new 4,4-difluoro-4-deoxyhexoses using a RCM-dihydroxylation sequence. In order to widen the range of available difluorinated monosaccharide analogues, a potentially highly enantioselective, non-RCM based route was developed. This approach relied on the use of (3-bromo-3,3-difluoro-prop-1-ynyl)-benzene as the fluorinated building block and Sharpless asymmetric dihydroxylations to introduce hydroxyl groups enantioselectively. Unfortunately, a poor choice of protecting group prevented access to the desired difluorinated monosaccharide analogues, even if the asymmetric dihydroxylation proved successful and enantioselective. RCM was also used to synthesise different types of difluorocyclooctenones from trifluoroethanol. These difluorinated 8-membered carbocycles showed interesting and unusual conformational behaviour and were investigated by NMR experiments and a simple computational study. These difluorocyclooctenones were also used to synthesise new bicyclic structures, which are effectively conformationally restrained difluorinated monosaccharide analogues.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.697250  DOI: Not available
Share: