Tomas, Marta Cavero; (1999) Aspects of thionitrites and nitric oxide in chemistry and biology. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis is divided into three parts: Part one is comprised of six chapters and provides a topical review of the main aspects of the chemistry and biology of nitric oxide and of thionitrites. The first chapter is a general introduction to the topic. The second chapter reviews the biology of nitric oxide. The third chapter provides a survey of some of the known chemistry of nitric oxide, with particular emphasis on those aspects which might be relevant in biological systems. The fourth chapter describes the biology of thionitrites in relation to NO. The fifth chapter describes in detail the chemistry of thionitrites, emphasising both those aspects which might be of biological importance and those which make the compounds of potential use in organic synthesis. The sixth chapter states the aims of the present project in the context of the current state of the field, as discussed in the preceding sections of the review. Part two describes the work that has been carried out during this thesis and is divided into 6 chapters. The first three chapters describe the initial results of our studies aimed at finding novel potential uses of thionitrites in organic synthesis, focusing on the thermal or photochemically induced addition of thionitrites onto olefins. Chapter 1 describes the synthesis of unsaturated thionitrites. Chapter 2 reports on the intramolecular cyclisation of thionitrites onto alkenes and its applications for the synthesis of episulfides and thiofuran compounds. Chapter 3 examines the inter-molecular version of this reaction, with particular emphasis on reactions involving trityl thionitrite, which was chosen as a model of a stable tertiary thionitrite. This thionitrite has been shown to add very efficiently to alkenes which contain an electron withdrawing or aromatic group and to conjugated dienes. The products obtained are the corresponding α-oximino sulfides. Chapters 4 and 5 describe the results obtained in studies towards achieving a better understanding of the reactivity of thionitrites in biological systems. Chapter 4 provides additional insight into the possible mechanism of NO release from bio-active thionitrites in vivo, by comparison of the biological activity of enantiomeric pairs of thionitrites in simple rat-artery models. On the other hand, the results discussed in Chapter 5 seem to indicate that a direct thionitrite-disulfide exchange reaction in solution systems which model physiological conditions does not take place. Finally, in Chapter 6, a series of overall conclusions have been drawn. Part three provides a formal description of the experimental results and procedures employed throughout this work and is divided into 6 chapters. The first chapter describes the general procedures. The remaining five chapters describe the experimental details corresponding to the work described in Chapters 1 to 5 of the second part.

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