Szpara, Rachel; (2022) The Selective Dehydration of Sugars in the Sustainable Synthesis of Chiral Fragments and Fluoroalkane Generation from Prochiral Substrates. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Waste biomass is abundant in sugars (both hexoses and pentoses), making them a renewable source of chiral building blocks which may be utilised in synthetic chemistry. Although large percentages of waste biomass are useful (~17% sugar by weight), large-scale production of drug precursors and THF-containing molecules often utilise alternative synthetic routes. Trapping of sugars in their open-chain form allows them to be treated as chiral polyol reagents for attaching chiral centres. A variety of different sugar thioacetals may be selectively dehydrated to produce the corresponding ketene thioacetals under mild basic conditions. The reactivity of the resulting ketene thioacetals has been explored, with cyclisation induced to produce a range of novel heterocycles. Further selective dehydration has been carried out in some cases. Insight into the mechanism of dehydration has been provided, with studies into the intermediate structures. With the demand for chiral heterocyclic rings increasing in pharmaceuticals, we present sustainable methods for the synthesis of useful compounds from innately chiral fragments. In addition, studies into the formation of chiral fluorine compounds have been explored, with the application of ene-reductase biocatalysis in an effort for a more sustainable approach to synthetic chiral fluorine generation.

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