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Title: Dispiroketals in asymmetric synthesis
Author: Innes, J. F.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1997
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This thesis is divided into five Chapters. The first consists of an introduction to dispiroketals and an overview of what has been achieved through their application in organic synthesis. The second Chapter describes the use of (2S,2'S)-2,2'-diphenyl-6,6'-bi-3,4-dihydro-2H-pyran to achieve the asymmetric synthesis of (+)-D-conduritol B. The synthesis proceeds in nine steps from DL-1-0,2-0:4-O,5-O-dicyclohexylidene-myo-inositol and the key step is the simultaneous protection and resolution of a racemic diol via dispiroketal methodology. The optical rotation of the final product, (+)-1D-Conduritol B, was found to differ significantly from literature reports, but the optical purity of our synthetic material was proved to be >98% using chiral gas chromatography. The third Chapter concerns work towards the synthesis of unsymmetrical bis-enol ethers and their use in dispiroketalisations. The synthetic approach to these compounds is a palladium-catalysed coupling of enol triflates with vinyl stannanes. Unusually, homocoupling of both partners was observed in addition to the desired heterocoupling but optimisation of conditions led to reasonable yields. The few dispiroketals possessing unsymmetrical alkyl substitution on the pyran rings are prepared. The fourth Chapter describes studies towards the development of an asymmetric reagent based on dispiroketals. A lithium aluminium hydride reduction modified with an enantioenriched dispiroketal-based diol gave a modest enantiomeric excess of product. A synthetic route to a dispiroketal-based secondary amine was developed in the racemic series, with a view to application of an enantioenriched version as a homochiral lithium amide base.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available