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Title: Studies towards the synthesis of the C1-C28 fragment of spongistatin 1
Author: Bamford, S. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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The thesis is divided into three Chapters. Chapter one consists of an introduction to marine natural products and a discussion of the isolation, structures and biological properties of the spongistatins. A presentation of previous syntheses of spiroketal-containing natural products followed by our proposed retrosynthesis of spongistatin 1 is then given. Chapter two describes the preparation of the C18-C17 epoxide via the coupling of the C8-C12 epoxide with the C13-C17 sulfone. Initial work in this area was directed towards the coupling of C13-C17 acyl anion equivalents with the C8-C12 epoxide, with a view to converting the relevant unmasked ketone into the desired C13 exo-methylene group. However, this route proved unsuccessful and the C13-C17 sulfone was coupled with the C8-C12 epoxide. Investigations were then performed towards introducing the C13 exo-methylene group, and reacting the anion of the coupled sulfone with Eschenmoser's salt followed by sodium amalgam-mediated elimination gave the product in good yield. The preparation of C1-C17 anomeric sulfones and the coupling with cinnamaldehyde is then discussed. All attempts to couple the anomeric sulfones with model epoxides and the C8-C17 epoxide were unsuccessful, thus an alternative approach using a C1-C7 dithiane was pursued. Several C1-C7 dithianes with varying protecting groups were then synthesised and the conditions for their coupling with epoxides were extensively screened. Finally, optimal conditions for the coupling of γ-oxygenated dithianes with a model epoxide were obtained, using the potassium diiospropylamide-lithium t-butoxide base system in a tetrahydrofuran/hexamethylphosphoramide solvent mixture. Chapter three contains a formal account of experiments and procedures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available