This thesis describes the development of nitro-Mannich/hydroamination cascade reactions for the synthesis of N-heterocycles, which are important motifs found in a variety of biologically active natural products and pharmaceuticals, such as atorvastatin (Lipitor®). Chapter 2 outlines the development of an efficient synthesis of 2,5-disubstituted pyrroles using a nitro-Mannich/hydroamination cascade. Starting from easily prepared N-protected imines and nitroalkyne substrates, a compatible combination of KOtBu (10 mol%) and AuCl3 (5 mol%) was used to afford the desired pyrrole products, after an alkene isomerisation/HNO2 elimination reaction sequence. Chapter 3 describes the extension of this methodology to the diastereo- and enantioselective synthesis of 1,2,3,4-tetrahydropyridine derivatives using a nitroalkyne substrate with an extended carbon chain. The sequential addition of a bifunctional Brønsted base/H-bond donor organocatalyst and a gold complex was found to facilitate the desired cascade reaction affording substituted 1,2,3,4-tetrahydropyridine products. We then established that highly substituted pyrrolidine compounds could be prepared by replacing the nitroalkyne substrate with a nitroallene substrate (Chapter 4). The combination of KOtBu (5 mol%) and a gold catalyst derived from Au(PPh3)Cl (10 mol%) and AgSbF6 (20 mol%) was found to give an efficient diastereoselective synthesis of pyrrolidine derivatives after an additional nitro group epimerisation step. In addition, the nitro-Mannich/hydroamination cascade using nitroallene substrates was developed into an enantioselective variant using the previously employed bifunctional Brønsted base/H-bond donor organocatalyst. This afforded enantioenriched pyrrolidine derivatives.

Increasing antibiotic resistance has created a need to develop rapid and reliable methods to identify bacteria and provide pertinent information to ensure suitable antibiotics or sugar therapeutics can be chosen for treatment. Carbohydrate structures attached to proteins on host cell surfaces provide a binding point for many pathogens, including bacteria. These structures can be mimicked using single monosaccharides glycosylated to alpha-hemolysin (alpha-HL). Alpha-HL is a beta-barrel pore-forming toxin secreted by Staphylococcus aureus that forms an SDS stable heptamer, which can be expressed by coupled in vitro transcription and translation and purified by polyacrylamide gel electrophoresis. The purified heptamers can be reconstituted into planar lipid bilayers and studied at the single channel level. Through single channel recordings the effects of sugar-linker lengths, different glycans and the interaction between the ‘Glycopore’ and sugar binding molecules can be studied. The glycopore, therefore, acts as a scaffold for analysing protein-sugar interactions. Studies in this thesis have focused on the synthesis of carbohydrates for site-selective protein glycosylation; cloning and in vitro transcription translation of alpha-HL monomers; and glycosylation and oligomerisation of alpha-HL to form glycopores suitable for lectin-binding studies. Lectins DC-SIGN and FimH have been expressed in Escherichia coli and these lectins as well as others have been screened using alpha-HL glycopores. The glycopores have also been investigated with bacteria in serum in a controlled molecule-specific manner using single-channel electrical recording. In this work glycosylated alpha-HL-monomers have been found to form stable heptamers which can be formed by oligomerisation on red blood cell membranes. The purified glycopores were reconstituted into planar lipid bilayers and studied at the single-channel level. Through single-channel recordings an optimised glycopore has been shown to be effective in distinguishing lectins alone and in a mixture and has afforded qualitative and quantitative information about the binding interactions between carbohydrates and sugar binding proteins. Furthermore, the glycopore has been used to sense bacteria which may provide an insight into modes of bacterial infection. In addition, a multivalent glycopore has been formed which has proved preliminary information about the effects of multivalency in lectin binding. The design and synthesis of non-beta-lactam antibiotic candidates and their evaluation has also been carried out.

This thesis explores roles of 2-oxoglutarate-dependent (2OG) oxygenases as interfaces that modulate steps in the flow of genetic information in cells in response to oxygen availability. Chapter 1 introduces mechanistic, biochemical and physiological aspects of major subfamilies of 2OG oxygenases, and their established regulatory roles in cells. In addition, structural and functional aspects of the ribosome and the translation process are discussed, with a focus on post-translational ribosome modifications. Chapter 2 investigates histone demethylases, which mediate chromatin-dependent regulation of gene expression and provides proof-of-concept for the rational, structure-guided design of small-molecules for selective inhibition of 2OG oxygenases with roles in cancer and inflammatory disease. Chapter 3 suggests regulatory roles for ten-eleven-translocation (TET)- catalysed DNA hydroxylation; calorimetric and thermal analyses reveal a duplex-stabilizing effect of the epigenetic 5-methylcytosine mark that is reversed upon conversion to 5- hydroxymethylcytosine (also termed the ‘sixth’ DNA base), raising the possibility that 2OG oxygenase catalysis might affect transcription via biophysical effects. Chapter 4 investigates fluoride release assays as a technology to enable medicinal chemistry studies on 2OG oxygenases with roles in fat mass regulation and obesity, cancer and inflammation; studies on the ALKBH5 enzyme show that it is a hypoxically upregulated 2OG oxygenase with a substrate preference distinct from previously characterized ALKBH enzymes. Chapter 5 identifies OGFOD1 as a 2OG-dependent ribosomal protein hydroxylase. OGFOD1 catalysis is conserved from yeast to humans. OGFOD1 catalyses formation of trans-3- hydroxy-L-proline in a highly conserved loop of ribosomal protein S23 proximal to the ribosomal decoding centre, possibly to modulate the interactions of eukaryotic ribosomes with tRNA, mRNA and translation factors in an oxygen-dependent manner. OGFOD1 is the functionally most well-conserved protein-modifying 2OG oxygenase; likewise, ribosomal protein S23 hydroxylation is the most well-conserved post-translational ribosome modification in eukaryotes. Some cell lines require OGFOD1 for proliferation, and scaffolds for OGFOD1- selective inhibitors are developed for use as potential antiproliferative agents and probes for cellular function. Chapter 6 shows the development of assays to investigate whether OGFOD1 catalysis affects ribosome assembly and function, including processivity, accuracy of initiation, elongation and termination, in yeast and mammalian cell lines. Chapter 7 concludes that ribosome hydroxylation might present an additional layer of regulatory complexity by which 2OG oxygenases could enable cells to respond to fluctuating oxygen levels.

Iminosugars, carbohydrate analogues in which nitrogen replaces the endocyclic oxygen, have attracted much interest due to their biological activity. Iminosugars inhibit carbohydrate-processing enzymes, thereby affecting many biological processes. Several iminosugars are licensed drugs, with many more compounds undergoing clinical trials. The main subject of this thesis is the synthesis and evaluation of novel iminosugars, particularly the effects of structural modifications on the biological activity of these compounds. Chapter 1 describes the role of carbohydrate-processing enzymes in the body, and explores the therapeutic applications of iminosugars that arise from their activity against these enzymes. Examples of substituted iminosugars are reviewed, and the effects of substituents on enzyme inhibition are described. Chapter 2 concerns methyl-branched swainsonine derivatives. Swainsonine has shown potential as a cancer treatment through its inhibition of α-mannosidase. The synthesis of (6R)- and (6S)-C-methyl D-swainsonine is described; both compounds were potent and selective α-mannosidase inhibitors (IC₅₀ 3.8 μM, 14 μM). Although less active than the parent compound, their selectivity for Golgi mannosidase over lysosomal mannosidase may be more important than the absolute value against the model enzyme. Chapter 3 describes the synthesis of a 2-C-methyl L-fucose derivative. A diastereoselective Kiliani reaction allowed the formation of a single lactone bearing a new quaternary centre. The utility of this intermediate in accessing di-branched iminosugars was explored; however, attempts to introduce nitrogen to the lactone lacked the necessary stereoselectivity. Chapter 4 relates to the synthesis of pyrrolidine iminosugars, specifically methyl amides. Two enantiomeric dihydroxyproline amides were synthesised; the D-proline derivative was a potent β-N-acetylhexosaminidase inhibitor (IC₅₀ values of up to 3.6 μM), but the L-enantiomer was completely inactive. Inhibition of N-acetylhexosaminidases is relevant to the treatment of cancer and lysosomal storage diseases, and this work contributed to a wider project investigating the effects of altered stereochemistry on the biological activity of pyrrolidine amides.

This thesis expands the scope for using the permethylpentalene ligand and its precursors in the synthesis of organometallic complexes. <strong>Chapter one</strong> begins with a brief review of linked metallocenes, with which multimetallic compounds bridged by pentalene ligands have often been compared, followed by a comprehensive review of the routes used to make pentalenes and substituted pentalenes. Organometallic compounds of pentalenes are introduced, with a focus on bimetallic systems. <strong>Chapter two</strong> explores the diversification of substituents added to the permethylpentalene (Pn*) precursor WeissH₄, to include ethyl and isopropyl groups. Low-symmetry mono-, di-, tri- and tetraalkylated products are formed, eight such organic molecules have been identified by NMR spectroscopy, and two characterised crystallographically. It has been demonstrated that subsequent hydrolysis and decarboxylation of two of these products produces low-symmetry alkylpentalene precursors. The chapter concludes with discussions on the selectivity exhibited in these reactions, and the assignment of stereochemistry. <strong>Chapter three</strong> describes the synthesis of the first homoleptic double metallocene complex of iron. Fe₂Pn*₂ has been characterised by X ray diffraction, and cyclic voltammetry studies demonstrate four accessible oxidation states (-1, 0, +1, +2). Magnetic measurements in the solid and solution state reveal an unusual triplet configuration, and DFT calculations indicate the origin of a high magnetic moment likely resides in unquenched orbital angular momentum contributions from SOMOs which have metal d character. Fe₂Pn*₂ is EPR silent at 5, 40, and 300 K both in solution and the solid state, suggesting a large zero-field splitting parameter. The reaction of the di-iron complex with carbon monoxide, ethylene and H2 is reported; the bimetallic CO adduct, Fe₂(&mu; &eta;⁵,&eta;³ Pn*)(&mu; &eta;⁵,&eta;¹ Pn*)(CO)₂, has been crystallographically characterised, and contains a highly distorted allylic bonding motif, which to the author’s knowledge is believed to be unique among iron complexes. <strong>Chapter four</strong> discusses the interaction of the bidentate Pn* ligand in anti bimetallic fused metallocenes. A new ligand exchange route has been developed to access the complexes (MCp)₂Pn* (M = Co, Ni), and the isostructural complexes (MCp*)₂Pn* have been made for M = Fe, Co, Ni by salt metathesis reactions. All five complexes have been characterised by single crystal X-ray crystallography, and have diamagnetic ground states in solution in common with their Pn bridged analogues. Variable temperature NMR studies reveal a spin-equilibrium between S = 0 and S = 1 in the dinickel complexes. DFT calculations reproduce the spin states found, and suggest the distortion towards &eta;³ coordination observed on crossing from Fe, to Co, to Ni, results from population of orbitals with M―bridgehead antibonding character. The electronic structures show it is important to draw comparisons between isoelectronic linked metallocenes. Electrochemical studies on the diiron, dicobalt, and (NiCp)₂Pn* complexes reveal at least three redox events for each. <strong>Chapter five</strong> documents the successful synthesis and characterisation of monometallic complexes of iron and manganese with Pn*H ligands. The isostructural complexes Fe(Pn*H)₂ and Mn(Pn*H)₂ can have been characterised crystallographically, and are potential precursors for accessing heterometallic, and multimetallic complexes. Mn(Pn*H)₂ is a rare example of a manganese sandwich compound and magnetic studies on a single isomer in the solution and solid states suggest it adopts intermediate spin states of S = 2 in solution, and S = 3/2 in the solid state. <strong>Chapter six</strong> gives experimental details for all syntheses and studies described in the preceding chapters. <strong>Chapter seven</strong> provides characterising data for all new compounds. Fitting data for VT NMR and SQUID studies are provided in the <strong>appendix</strong> at the end of this thesis. Crystallographic data in the form of .cif files, DFT output files, and raw SQUID data, can be found in the <strong>electronic appendix</strong>.

Analogues of Antibacterial Natural Products Elizabeth Anne Heaviside, St Catherine’s College, University of Oxford DPhil Thesis, Trinity Term 2012 This thesis is concerned with the synthesis and biological evaluation of structural mimics for the natural products 16-methyloxazolomycin and lemonomycin which display potent biological activity including antibacterial and antitumour activity. Chapter 1 explores methods and approaches to the discovery of new antibacterial drugs and the challenges faced in this respect. It also gives an overview of the properties of the natural products investigated in the following chapters and summarises previous synthetic approaches to these molecules published in the scientific literature. Chapter 2 describes the work carried out towards the synthesis of the diazabicyclo[3.2.1]octane unit of the tetrahydroisoquinoline antitumour antibiotic lemonomycin. The intended retrosynthesis of the natural product led to a 2,5-disubstituted pyrrolidine bearing a 1ʹ-amino functional group; a series of routes were explored for the synthesis of this unit. Using (S)-pyroglutamic acid, strategies using Eschenmoser and thiolactim ether coupling reactions were investigated. A sequence based on the formation of a pyrrolidine ring from the cyclisation of an appropriately substituted oxime ether derived from L-phenylalanine was then implemented but a competing Beckmann rearrangement/Grob fragmentation prevented access to the desired heterocycle. Preliminary investigations were also carried out on the modification of cyclic imines derived from oxime ethers which did not undergo Beckmann rearrangement. Chapter 3 describes the synthesis of a library of densely functionalised tetramic acid and pyroglutamate mimics for the right-hand fragment of 16-methyloxazolomycin, and their coupling with a gem-dimethylamide unit mimicking the middle fragment of the natural product. Tetramates were accessed through the Dieckmann cyclisation of N-acyloxazolidines and were derivatised with various alkyl halides. The pyroglutamates were accessed via the highly diastereoselective aldol cyclisation of N-acyloxazolidines formed by the amide coupling of a threonine derived oxazolidine and β-keto-acids. A series of β-keto-acids were synthesised through the acylation and subsequent ring-opening/decarboxylation reaction of Meldrum’s acid. The formation of right-hand/middle fragment adducts was explored using cycloaddition, alkylation and Sonogashira chemistry before a Wittig protocol led to the formation of adducts (E)- and (Z)- 402 and 403. Biological evaluation of the compounds synthesised in this chapter was carried out using both broth and hole-plate bioassays and active compounds were identified. Of particular note was that the Wittig adducts displayed a higher level of activity against Gram-negative E. coli than either the pyroglutamate or amide motifs alone.

Tunicamycins are potent antimicrobial agents but are also toxic to mammalian cells, which render them clinically impractical to use to treat infectious diseases. Instead, they have been used extensively as biochemical tools to study the N-linked glycosylation of proteins. However, despite such a routine application, their inhibitory mechanisms are still not clear. The central objective of this thesis was to develop novel tunicamycin analogues that are non-toxic to eukaryotic cells that could serve as potential antimicrobial drug candidates. We hypothesised that if we retain the lipid character of tunicamycin structure and modify the GlcNAc moiety then the antimicrobial activity would be retained but the tunicamycins inhibitory action towards GPT would be abolished, thus diminishing tunicamycins cytotoxicity towards mammalian cells. <b>I - Semi-synthesis of the Tunicamycin Core Scaffolds and Lipid Analogues</b> Semi-synthetic strategies were devised for isolating tunicamycin core scaffolds and for the selective addition of lipid chains at the 10'-N and 2"-N positions of tunicamycin, yielding the first library of novel tunicamycin lipid analogues. <b>II - Biological Evaluations of the Tunicamycin Core Scaffolds and Lipid Analogues</b> For the first time, the antibacterial activity of tunicamycins was shown to be dependent on the presence of a lipid chain. The tunicamycin core scaffolds were shown to lack antibacterial activity and cytotoxicity. More importantly, the library of tunicamycin lipid analogues with lipid chain length from seven to twelve carbons showed titrated antibacterial activity profile. Furthermore, the tunicamycin lipid analogues were not only found to have potent antibacterial and anti-M. tuberculosis activities but were non-cytotoxic compared to tunicamycins. The relative therapeutic index calculated for the tunicamycin lipid analogues was up to several thousand folds more than tunicamycins. <b>III - Investigation of the tunB and tunF Knockout in the tun Gene Cluster</b> The tunB and tunF single knockout mutations were made in the tun gene cluster by PCR-targeting and then heterologously expressed in S. coelicolor. The tunB knockout successfully abolished tunicamycin biosynthesis and showed evidence by MS the first existence of exo-glycal intermediates in sugar biology, further supporting the discovery of TunA as a novel NDP-sugar 5,6-dehydrogenase. <b>IV - Investigation of the TunD and TunE Enzymatic Activities in Tunicamycin Biosynthetic Pathway</b> The recapitulation of TunD glycosyltransferase and TunE deacetylase activities in vitro were attempted. Recombinant TunD was refolded from insoluble TunD inclusion bodies, while TunE was isolated in small quantities. However, no TunD and TunE activities were found using proposed intermediates. The co-translation of the tun gene cluster and the formation of multi-protein complex are proposed to be involved in the tunicamycin biosynthesis.

Este trabalho apresenta: 1) Duas revisões bibliográficas sendo uma sobre a síntese de &#945;-ceto-tioésteres e -ésteres e a outra sobre a decomposição de sulfóxidos e sulfonas sulfeniladas; 2) Investigações prévias indicando a viabilidade da decomposição térmica e a estabilidade relativa dos derivados bissulfenilados de tioésteres de diferentes estados de oxidação Ia-e, obtidos a partir do &#945;-ceto-tioéster; 3) O estudo de síntese de precursores de &#945;-ceto-tioésteres II e &#945;-ceto-ésteres III, a saber: &#945; - metilsulfonil- &#945; - metiltio tioésteres IVa-c, -éster V e &#945;, &#945; - dimetiltio - ésteres VIa-c; 4) Decomposição térmica de &#945;-metilsulfonil-&#945;-metiltio-tioésteres Iva, b e c e -éster V sintetizados aos &#945;-ceto-tioésteres e ésteres correspondentes, pelo emprego do método elaborado anteriormente por Wladislaw e col. e sugestão do mecanismo da mesma. A síntese de &#945; metilsulfonil &#945; metiltio tiopropionato de etila (Ivb), foi efetuada a partir do ácido &#945;-cloro propiônico através de quatro passos reacionais, a saber: sulfenilação por substituição, oxidação à sulfona , tioesterificação e sulfenilação pelo emprego de NaH/MeS02SMe em DMSO. A obtenção do &#945; - benzil - &#945; - metilsulfonil - &#945; - metiltio - tioacetato de etila (Ivc) foi efetuada a partir de ácido &#945;-cloro acético através de reações de sulfenilação por substituição oxidação à sulfona tioesterificação alquilação com brometo de benzila e NaH em DMSO e, finalmente, a sulfenilação que só foi possível com o emprego de N-metiltioftalimida. A síntese de &#945;-metilsulfonil-&#945;-metiltio-propionato de etila (V) foi efetuada a partir do &#945;-metilsulfonil malonato VIIa pelo eemprego do método de descarbetoxilação sulfenilativa usando 1,4 diazabiciclo [2,2,2] octano (DABCO) em tolueno sob refluxo e MeSO2SMe. Os compostos VIIa,b e c foram preparados a partir dos malonatos de dietila alquil - substituidos, seguido de sulfenilação e oxidação à sulfona. É de interesse a inédita reação de &#945; - metilsulfonil fenilmalonato de dietila (VIIb), com DABCO em benzeno sob refluxo e MeSO2SMe, que conduziu à dessulfonilação sulfenilativa fornecendo o &#945; - metiltio - fenilmalonato de dietila. É apresentada uma discussão mecanística tanto sobre descarbetoxilação, como sobre dessulfonilação sulfenilativas. A síntese de &#945;,&#945;-dimetiltio-ésteres VIa-c foi efetuada pela reação de sulfenilação com descarboxilação dos mono-ácidos malônicos correspondentes. O acompanhamento da descarboxilação e experimentos de deuteração permitiram esclarecer a sequência dos passos reacionais nestas novas reações. Cabe ressaltar que são compostos ainda não descritos na literatura os precursores IVa, IVb, IVc, V e Vib e 11 intermediários envolvidos nas reações efetuadas. Os resultados apresentados neste trabalho, além de importância sintética, trazem uma contribuição para a Química de Compostos Orgânicos de Enxofre. / This work presents: 1) Two literature reviews, one about the synthesis of &#945;-keto thioesters and esters and the other on the decomposition of sulfenylated sulfoxides and sulfones; 2) Previous investigations indicating the viability of thermal decomposition and the relative stability of the dithioderivatives of different oxidation states Ia-e,which were obtained from the &#945;-keto thioester; 3) The study of synthesis of &#945;-keto thioesters II and esters III precursors, which are the following: &#945;-methylsulfonyl-&#945;-methylthio-thioesters IVa-c and -ester V, and &#945;, &#945; - dimethylthio esters VIa-c; 4) Thermal decomposition of the synthesized &#945; - methylsulfonyl- &#945; -methylthio- thioesters Iva,b e c and ester V, to the corresponding &#945;-keto thioesters and &#945;-keto ester, through the method developed by Wladislaw et al., with the suggestion of the mechanism. &#945;-Methylsulfonyl-&#945;-methylthio ethyl thiopropionate (Ivb) was synthesized from &#945;-chloro-propionic acid in four steps: sulfenylative substitution, oxidation to sulfone, thioesterification and sulfenylation using NaH/MeSO2SMe in DMSO. &#945;-Benzyl-&#945;-methylsulfonyl-&#945;-methylthio ethyl thioacetate (,i>Ivc) was obtained from &#945;-chloro acetic acid through the following steps: sulfenylative substitution, oxidation to sulfone, thioesterification, alkylation with benzylbromide and NaH in DMSO, and finally, the sulfenylation which was successful only with the use of N-methylthiophtalimide. &#945;-Methylsulfonyl-&#945;-methylthio ethyl propionate (V) was synthesized through the sulfenylative decarbethoxylation of &#945; methylsulfonyl diethyl malonate VIIa employing DABCO (1,4-diazabicyclo [2.2.2.]octane), in refluxing toluene, and MeSO2Sme. The compounds VIIa,b e c were obtained by the alkylation of malonates, followed by sulfenylation and oxidation to sulfones. An interesting and novel reaction, the sulfenylative desulfonylation, was observed when &#945;-methylsulfonyl phenyldiethyl malonate (VIIb) was treated with DABCO, in refluxing benzene and MeSO2SMe, which led to the &#945;-methylthio diethyl malonate. A mechanistic discussion about the sulfenylative decarbethoxylation and sulfenylative desulfonylation is presented. &#945;, &#945;-dimethylthio esters VIa-c were synthesized by sulfenylation and decarboxylation of the corresponding malonic half-esters. The sequence of the steps of this new reaction could be determined by deuteration experiments and by following the evolution of CO2. The precursors IV, IVb, IVc, V e Vib and 11 intermediates were unknown compounds. This work, besides the synthetical importance, presents some contribution to the Organosulfur Chemistry.

Este trabalho apresenta: 1) Duas revisões bibliográficas sendo uma sobre a síntese de &#945;-ceto-tioésteres e -ésteres e a outra sobre a decomposição de sulfóxidos e sulfonas sulfeniladas; 2) Investigações prévias indicando a viabilidade da decomposição térmica e a estabilidade relativa dos derivados bissulfenilados de tioésteres de diferentes estados de oxidação Ia-e, obtidos a partir do &#945;-ceto-tioéster; 3) O estudo de síntese de precursores de &#945;-ceto-tioésteres II e &#945;-ceto-ésteres III, a saber: &#945; - metilsulfonil- &#945; - metiltio tioésteres IVa-c, -éster V e &#945;, &#945; - dimetiltio - ésteres VIa-c; 4) Decomposição térmica de &#945;-metilsulfonil-&#945;-metiltio-tioésteres Iva, b e c e -éster V sintetizados aos &#945;-ceto-tioésteres e ésteres correspondentes, pelo emprego do método elaborado anteriormente por Wladislaw e col. e sugestão do mecanismo da mesma. A síntese de &#945; metilsulfonil &#945; metiltio tiopropionato de etila (Ivb), foi efetuada a partir do ácido &#945;-cloro propiônico através de quatro passos reacionais, a saber: sulfenilação por substituição, oxidação à sulfona , tioesterificação e sulfenilação pelo emprego de NaH/MeS02SMe em DMSO. A obtenção do &#945; - benzil - &#945; - metilsulfonil - &#945; - metiltio - tioacetato de etila (Ivc) foi efetuada a partir de ácido &#945;-cloro acético através de reações de sulfenilação por substituição oxidação à sulfona tioesterificação alquilação com brometo de benzila e NaH em DMSO e, finalmente, a sulfenilação que só foi possível com o emprego de N-metiltioftalimida. A síntese de &#945;-metilsulfonil-&#945;-metiltio-propionato de etila (V) foi efetuada a partir do &#945;-metilsulfonil malonato VIIa pelo eemprego do método de descarbetoxilação sulfenilativa usando 1,4 diazabiciclo [2,2,2] octano (DABCO) em tolueno sob refluxo e MeSO2SMe. Os compostos VIIa,b e c foram preparados a partir dos malonatos de dietila alquil - substituidos, seguido de sulfenilação e oxidação à sulfona. É de interesse a inédita reação de &#945; - metilsulfonil fenilmalonato de dietila (VIIb), com DABCO em benzeno sob refluxo e MeSO2SMe, que conduziu à dessulfonilação sulfenilativa fornecendo o &#945; - metiltio - fenilmalonato de dietila. É apresentada uma discussão mecanística tanto sobre descarbetoxilação, como sobre dessulfonilação sulfenilativas. A síntese de &#945;,&#945;-dimetiltio-ésteres VIa-c foi efetuada pela reação de sulfenilação com descarboxilação dos mono-ácidos malônicos correspondentes. O acompanhamento da descarboxilação e experimentos de deuteração permitiram esclarecer a sequência dos passos reacionais nestas novas reações. Cabe ressaltar que são compostos ainda não descritos na literatura os precursores IVa, IVb, IVc, V e Vib e 11 intermediários envolvidos nas reações efetuadas. Os resultados apresentados neste trabalho, além de importância sintética, trazem uma contribuição para a Química de Compostos Orgânicos de Enxofre. / This work presents: 1) Two literature reviews, one about the synthesis of &#945;-keto thioesters and esters and the other on the decomposition of sulfenylated sulfoxides and sulfones; 2) Previous investigations indicating the viability of thermal decomposition and the relative stability of the dithioderivatives of different oxidation states Ia-e,which were obtained from the &#945;-keto thioester; 3) The study of synthesis of &#945;-keto thioesters II and esters III precursors, which are the following: &#945;-methylsulfonyl-&#945;-methylthio-thioesters IVa-c and -ester V, and &#945;, &#945; - dimethylthio esters VIa-c; 4) Thermal decomposition of the synthesized &#945; - methylsulfonyl- &#945; -methylthio- thioesters Iva,b e c and ester V, to the corresponding &#945;-keto thioesters and &#945;-keto ester, through the method developed by Wladislaw et al., with the suggestion of the mechanism. &#945;-Methylsulfonyl-&#945;-methylthio ethyl thiopropionate (Ivb) was synthesized from &#945;-chloro-propionic acid in four steps: sulfenylative substitution, oxidation to sulfone, thioesterification and sulfenylation using NaH/MeSO2SMe in DMSO. &#945;-Benzyl-&#945;-methylsulfonyl-&#945;-methylthio ethyl thioacetate (,i>Ivc) was obtained from &#945;-chloro acetic acid through the following steps: sulfenylative substitution, oxidation to sulfone, thioesterification, alkylation with benzylbromide and NaH in DMSO, and finally, the sulfenylation which was successful only with the use of N-methylthiophtalimide. &#945;-Methylsulfonyl-&#945;-methylthio ethyl propionate (V) was synthesized through the sulfenylative decarbethoxylation of &#945; methylsulfonyl diethyl malonate VIIa employing DABCO (1,4-diazabicyclo [2.2.2.]octane), in refluxing toluene, and MeSO2Sme. The compounds VIIa,b e c were obtained by the alkylation of malonates, followed by sulfenylation and oxidation to sulfones. An interesting and novel reaction, the sulfenylative desulfonylation, was observed when &#945;-methylsulfonyl phenyldiethyl malonate (VIIb) was treated with DABCO, in refluxing benzene and MeSO2SMe, which led to the &#945;-methylthio diethyl malonate. A mechanistic discussion about the sulfenylative decarbethoxylation and sulfenylative desulfonylation is presented. &#945;, &#945;-dimethylthio esters VIa-c were synthesized by sulfenylation and decarboxylation of the corresponding malonic half-esters. The sequence of the steps of this new reaction could be determined by deuteration experiments and by following the evolution of CO2. The precursors IV, IVb, IVc, V e Vib and 11 intermediates were unknown compounds. This work, besides the synthetical importance, presents some contribution to the Organosulfur Chemistry.

<strong>Chapter 1</strong> Provides an overview of drug discovery with particular emphasis on library selection and hit identification methods using virtual based approaches. <strong>Chapter 2</strong> Gives an outline of the bone morphogenetic protein (BMP) signalling pathway and literature BMP pathway modulators. The association between the regulation of BMP pathway and cardiomyogenesis is also described. <strong>Chapter 3</strong> Describes the use of ligand based virtual screening to discover small molecule activators of the BMP signalling pathway. A robust cell based BMP responsive gene activity reporter assay was developed to test the libraries of small molecules selected. Hit molecules from the screen were synthesised to validate activity. It was found that a group of known histone deacetylase (HDAC) inhibitors displayed most promising activity. These were evaluated in a secondary assay measuring the expression of two BMP pathway regulated genes, hepcidin and Id1, using reverse transcription polymerase chain reaction (RT-PCR). 188 was discovered to increase expression of both BMP-responsive genes. <strong>Chapter 4</strong> Provides an overview of existing cannabinoid receptor (CBR) modulating molecules and their connection to progression of atherosclerosis. <strong>Chapter 5</strong> Outlines the identification and optimisation of selective small molecule agonists acting at the cannabinoid 2 receptor (CB₂R). Ligand based virtual screen was undertaken and promising hits were synthesised to allow structure activity relationship (SAR) to be developed around the hit molecule providing further information of the functional groups tolerated at the active site. Subsequent studies led to the investigation and optimisation of physicochemical properties around 236 leading to the development of a suitable compound for in vivo testing. Finally, a CB₂R selective compound with favourable physicochemical properties was evaluated in vivo in a murine inflammation model and displayed reduced recruitment of monocytes to the site of inflammation.