Streptomyces, the largest genus of Actinobacteria, are renowned for their ability to produce a wide variety of specialised metabolites, including many clinically used antibiotics and other bioactive natural products. Biosynthesis of these specialised metabolites is often tightly regulated by transcriptional regulators, some of which are responsive to signalling molecules, e.g., 2-alkyl-4-hydroxymethylfuran-3-carboxylic acids (AHFCAs), thus initiating a series of regulatory events. The biosynthetic role of MmfL in AHFCA assembly has been investigated in vitro using a synthetic substrate. MmfL has been shown to catalyse an AfsA-like reaction, involving condensation of an ACP-bound β-ketothioester and dihydroxyacetone phosphate to form a phosphorylated butenolide intermediate. The interactions between DNA, AHFCA ligands and ArpA-like repressors, MmfR and SgnR, have been investigated in vitro using electrophoretic mobility shift assays. This work leads to a better understanding of the regulation mechanism in specialised metabolite biosynthesis. Heterologous expression of a putative pyochelin-like gene cluster, sven0503-sven0517 from S. venezuelae ATCC 10712, has previously been shown to result in the production of thiazostatin and watasemycin as the main metabolic products of the cluster. Isopyochelin, a structural isomer of pyochelin, was also identified and characterised by comparison with synthetic standards. Sven0516 has previously been identified as the thiazoline reductase required for the biosynthesis of all of the metabolic products of the cluster. The class B radical SAM methylase Sven0515 was shown to be responsible for the methylation of thiazostatin to give watasemycin. This is the first experimentally validated example of such a reaction in the biosynthesis of a nonribosomal peptide. From incorporation experiments using stereospecifically deuterium-labelled cysteine, it has been demonstrated that Sven0515-mediated methylation proceeds with abstraction of the pro-R hydrogen atom and results in inversion of stereochemistry at the methylating position. The absolute stereochemistry of thiazostatin and watasemycin has been reassigned on the basis of the absolute configuration determined for isopyochelin.

This thesis is a summary of the work carried out exploring the properties and applications of calix[4]arene ligands. Particular attention is given to the flexibility and encapsulation capabilities of these species. Initially synthetic methodology for the incorporation of bisimidazolinium and imidaolium groups was targeted. The synthesis of imidazolinium functionalised species proved problematic, however pro-ligand 2a-2HI was readily prepared via a six-step synthetic procedure. The coordination chemistry of 2a-2HI with [Rh(COD)Cl]2 and [Rh(CO)2Cl]2, via generation of the free carbene (2a) or transmetallation from an isolated silver complex (6a) was explored. Both routes resulted in the formation of bimetallic species. The isolation of these complexes highlights the flexibility of the calix[4]arene scaffold. The role of the calix[4]arene was probed though comparison to complexes of the monodentate IiPr2Me2 ligand. Based on these results, the imidazole-2-thione (NHCS) ligand 3 was derived from 2a and elemental sulfur. Monodentate rhodium and iridium complexes of 3 were readily prepared and found to bind potassium cations within the calix[4]arene cavity. This unusual host-guest chemistry was probed by 1H NMR spectroscopy and in the solid state through comparison to other calix[4]arene hosts.

Since the discovery of zinc as an essential element for living organisms including humans, animals, plants, fungi and bacteria, much has been learnt about zinc in biological systems, ranging from its effects at the whole organism level, including the uptake/efflux of zinc, identification of important zinc-regulator proteins, down to structural, thermodynamic, and kinetic details of zinc-protein interactions. One of the most exciting fields to work on, currently, is understanding the importance of zinc “on the move” - in particular the “acquisition and homeostasis” of this micronutrient element by the organisms. In this wider context, zinc homeostasis by open ocean cyanobacteria, which occupy variable ecosystems with an erratic nutrient supply, has become of recent interest. In an attempt to resolve how open ocean cyanobacteria persist in regions where the zinc concentration is thought to be limited, we hypothesised that the cyanobacterium Synechococcus sp. WH8102 might provide an extracellular zinc scavenger for the acquisition of this essential element. Therefore, the current study developed a method to isolate and purify the putative biogenic zinc-binding ligand (zincophore) using polystyrene-divinylbenzene resin and liquid chromatographies. However, it seems likely Synechococcus sp. WH8102 produce ligands that can bind to zinc only under zinc-depleted conditions. Then, we performed zinc limitation and repletion experiments on axenic cultures of marine Synechococcus sp. WH8102, and data determined that this strain mounted an adaptive response for zinc under depleted and replete conditions, resulting in the induction and/or repression of a number of proteins. As a homologue to the Fur family, Zur from Synechococcus sp. WH8102 was sub-cloned and purified in the absence of zinc ions in the cultures. Synechococcus sp. WH8102 Zur protein at neutral pH (~pH 7.8), in mass spectrometry, presented as a mixture of species including a monomer with two zinc ions bound Zn2Zur, a dimer with four zinc ions bound, and another well folded Zn4Zur2 dimer. The complementary technique, ICP-OES, confirmed that the zinc binding stoichiometry was in agreement with mass spectrometric findings, 2.1±0.2 Zn(II) ions per monomer. Mimicking a drop in available cellular zinc as may be expected in zinc-deplete conditions, it was found that only one of the two metal ions bound per monomer was removed by EDTA from Synechococcus sp. WH8102 Zur protein, giving 0.9 ± 0.3 Zn(II) atoms per monomer, with shifting in the monomer/dimer equilibrium toward Zn1Zur species. No large difference in the secondary structure between the metallo-species of the SynZur protein was found in CD spectroscopy. Moreover, Synechococcus sp. WH8102 Zur protein was found to behave in a similar manner to previously studied Fur family proteins, where zinc removal from the sensory site is fully reversible and has the ability to re-establish a (2:1) Zn(II):protein ratio in less than 15 min with 1.9 ± 0.4 Zn(II) atoms per monomer. Similarly, Synechococcus sp. WH8102 Zur was found to act as a transcriptional factor in the presence of zinc ions and bind specifically to 23 AT-rich DNA sequence. The “free” cytosolic zinc concentrations that Zur protein trigger transcription of znuABC and smtA found to be in femtomolar range ~ 1.78 ×10-15, with the dissociation constant ~ 62.65±1.47 nM and 61.76 ± 2.42 nM for Zur-PznuA promoter and SynZur-PsmtA promoter, respectively.

Solid state nuclear magnetic resonance (NMR) is a powerful probe of inorganic materials systems. Through carefully changing materials compositions and synthesis methods, the impact on the local structure can be investigated. These have been applied to three main materials sectors: Paramagnetic materials in NMR have traditionally suffered from poor resolution due to broadening experienced at the nuclei from localised unpaired electrons. In this work, a fast magic angle spinning (MAS) and low field approach has been applied to these paramagnetic cathode materials to improve this resolution, and elucidate structural information from the investigated materials. The resolution gained from these techniques has been used to highlight differences observed in the 7Li shifts of lithium iron phosphate (LFP) produced by different synthesis techniques. This was found to be related to the cell volume of the LiFePO4 phase. Furthermore, the investigation of V doped LFP by 7Li and 31P MAS NMR has resulted in the observation of many common impurities resulting from synthesis. Additionally, 31Presonances could be identified that were related to V near the phosphorus site, indicating successfully doping in some of the higher Li containing samples. Through 29Si and 17O MAS NMR, changes in the local structure between Ca and Zn doped Stöber nanoparticles are observed. Similarly to other Ca containing materials, incorporation of Ca into the Stöber network has been shown to disrupt Sibridging bonds promoting the formation of non-bridging bonds in the silica network. However, addition of Zn tells a different story. This is first observed in the static measurements, where incorporation of high amounts of Zn leads to no evidence of hydroxyls observed in the Stöber network. Whereas, high resolution transmission electron microscopy (HRTEM) and density functional theory (DFT) calculations confirm the presence of crystalline Zn2SiO4 -II in the nanoparticles. Finally, activation of two series of synthetic sodium- and aluminium substituted calcium silicate hydrate (C-(N)-(A)-S-H) geopolymers are investigated. Increasing the CaO has been shown to increase the disorder of the silica network, and also to promote the increase of crystallinity of the systems through observation of calcium aluminate phases. Additionally, increasing the amount of aluminium relative to the silicon in the system, promotes more of these crystalline phases to form.

N-Methylwelwitindolinone C isothiocyanate (7), isolated from the blue green algae Hapalosiphon welwitschii and Westiella intricate, is a structurally novel alkaloid related to the welwitindolinone family. This thesis describes studies towards the total synthesis of this natural product. Chapter One introduces the biological activities and the proposed biosyntheses of the welwitindolinone alkaloids. The synthetic studies towards the synthesis of this class of natural products will be also discussed. Chapter Two describes the different strategies towards the synthesis of a bicyclo[4.3.1]decane scaffold possessing a gem-dimethyl group present in the natural product 7. The geminal group was envisioned via a methyl addition to a carbonyl, a deprotonation of a sulfone or an intramolecular Michael addition. Generation of the desired skeleton 182 was achieved by using an intramolecular palladium-catalysed α-arylation of a trimethylsilyl enol ether. Chapter Three describes various attempts to the direct installation of a nitrogen functionality at the bridgehead position. In an indirect mode, a regioselective deprotonation allowed functionalisation of the desired bridgehead position and the access to isocyanate 297 and diketoazide 276, respectively obtained from a [3,3]-sigmatropic rearrangement and an aza- Michael reaction. A three step sequence involving a regioselective deprotonation of diketoazide 276, followed by aldol condensation and dehydration led to the advance intermediate 306. Chapter Four describes the recent breakthrough in the synthesis of the welwitindolinone alkaloids. The total synthesis of N-methylwelwitindolinone D isonitrile (19) and N-methylwelwitindolinone C isothiocyanate (7), along with related studies reported this year. Chapter Five includes the experimental procedures and analytical data for the preparation of novel compounds described during the course of this study.

The thermal decomposition of mixed cation amides, Li\(_3\)Na(NH\(_2\))4 and LiNa\(_2\)(NH\(_2\))\(_3\), with light metal hydrides, lithium hydride, sodium hydride and magnesium hydride, was investigated and hydrogen gas was identified as the major desorption product in all cases. Minimal ammonia was detected and therefore the mixed cation amides could be considered as hydrogen storage materials. The reactions were found to be similar to previously studied light metal amide-hydride systems like lithium amide/lithium hydride and lithium amide/magnesium hydride. Magnesium hydride caused the hydrogen desorption from the mixed cation amides to occur at a lower temperature than when they were heated with lithium hydride. The hydrogen desorption was also at a lower temperature than LiNH\(_2\) + LiH and 2LiNH\(_2\) + MgH\(_2\). Although hydrogen was desorbed when the mixed cation amides were heated with NaH, the amount was much smaller than for LiH and MgH\(_2\), therefore making it less suitable as a hydrogen storage material. Reactions in various ratios between NaNH\(_2\) and MgH\(_2\) were investigated to intermediate temperatures up to 350 °C. Thermal decomposition, Raman spectroscopy and thermogravimetric analysis were all employed to explore the decomposition and reaction pathways of these reactions. It was found that the products were analogous to those formed by lithium amide heated with magnesium hydride in similar ratios. The more hydride included in the reaction, the greater the hydrogen loss for the products. Three new phases were identified and each was attempted to be made pure in order to characterise them. Evidence for the formation of a mixed Na-Mg amide, Na-Mg imide and Na-Mg nitride, under different temperatures and reaction conditions, was obtained. Attempts to rehydrogenate the Na-Mg imide were successful, reforming magnesium amide and sodium hydride. Sodium amide(NaNH\(_2\)) has been relatively neglected in the literature and so an examination of its decomposition products and reaction with sodium hydride, as a comparison to LiNH\(_2\)-LiH, were carried out. Using Raman and thermal decomposition techniques, it was proposed that a sodium imide may be formed, possibly with the same variable stoichiometry as observed for LiNH\(_2\)-Li\(_2\)NH. Rehydrogenation was attempted on this phase, but was unsuccessful.

In this thesis the development of several novel gold-catalysed transformations are reported. Two intermolecular atom transfer processes have been designed and developed to access gold carbenoid reactivity. The latter reactive species allowed the synthesis of various α,ß-unsaturated carboxylic acid derivatives and trisubstituted oxazoles. Numerous nitrogen- and oxygen substituted alkynes have been prepared and employed in oxygen transfer processes promoted by gold complexes. Using pyridine \(N\)-oxide, both ynamides and ynol ethers underwent regioselective intermolecular oxidation reactions under mild gold catalysis conditions. During the transformation, an α-oxo gold carbenoid intermediate is accessed which develops through a rapid 1,2-insertion reaction to yield α,ß -unsaturated imides and vinylogous carbimates. The strategy has proved to be a valid alternative to the use of hazardous α-oxo diazo compound when carbene reactivity is desired. Appling a similar strategy, \(N\)-imido pyridonium ylides have been used as an \(O,N\)-dipole onto gold activated ynamides and ynol ethers. The overall [3+2] cyclisation occurred through a nitrene transfer process followed by a cycloisomerisation step. Under this approach, ynamides and ynol ethers have been converted into highly functionalised trisubstituted oxazoles. The mild gold catalysis conditions allowed the use of a wide range of functionality. Moreover, the α-imido gold carbenoid involved as a reaction intermediate displayed the possibility to utilise such protocol to access α-imido carbene reactivity

Chiral sensing is a challenging field for the chemist. Not many sensors for chiral recognition have been studied, and only a few examples of electrochemical chiral sensors are known in the literature. The aim of this project was to synthesise novel ferrocenyl-based chiral receptors, and to study their applications for chiral sensing in solution or upon incorporation onto gold surfaces as self-assembled monolayers (SAMs). From the solution studies it was possible to gain further information on the electrochemical behaviour of ferrocenyl-based receptors during the sensing of chiral carboxylates. The incorporation of receptors onto electrode surfaces led to an economy on the amount of compound required and higher sensitivity in analyte detection. However, the chiral recognition properties and the stability of the SAMs still need to be improved. Multifunctional receptors containing BINOL and ferrocenyl reporting groups were investigated to compare the use of electrochemistry and fluorescence spectroscopy in the chiral recognition of carboxylic acids, amino acid derivatives, or amino acid anions. Finally, a DNA analogue in which ferrocenyl units were incorporated in the backbone was studied. The electrochemical properties of this system as a single strand and in its interaction with complementary strands of DNA and PNA were investigated.

Dictyoxetane, a structurally novel diterpene, is related to the dollabellane class of natural products. Dictyoxetane contains a dioxatricyclic subunit that has never been encountered in any other natural product. This thesis describes studies towards a first total synthesis of dictyoxetane, based on a proposed intramolecular Paternò-Büchi [2+2] photocyclisation reaction between a ketone and a cyclic enol ether to generate the oxetane heterocycle of the natural product. Chapter 1 introduces the dolabellanes. The isolation, structure and proposed biosynthesis of dictyoxetane are discussed, along with existing synthetic studies towards the core dioxatricyclic ring system. Key aspects of the Paternò-Büchi reaction of alkenes with carbonyl compounds are presented. In Chapter 2 a model system, designed to test the key Paternò-Büchi [2+2] photocyclisation reaction, is proposed. A number of strategies are investigated for the overall conversion of the double bond of isopulegol into a six-membered ring enol ether. Chapter 3 describes studies towards the synthesis of the [4.3.0]-trans-hydrindane ring system contained within dictyoxetane, a structural feature that has yet to be addressed in the literature. Chapter 4 contains the experimental procedures and analytical data of all compounds prepared during the course of this study.

Alkylidene carbenes are reactive intermediates in organic chemistry. Intramolecular 1,5 C-H insertion reactions lead to cyclopentenes with retention of configuration. Insertions into O-Si or O-H bonds form dihydrofurans. Chapter 1 reviews of the chemistry of alkylidene carbenes, focusing on their reactivity and the techniques that can be employed for their in situ generation. Factors governing the selectivity of these reactive intermediates are discussed. Previous investigations in the Grainger group on the use of alkylidene carbenes in model studies towards the synthesis of the cyclopentene A-ring of ingenol, a biologically active diterpene, are described. Chapter 2 describes an investigation into hydroxycyclopentene annulation using the 1,5 C-H insertion reaction of α-hydroxyalkylidene carbenes on a 2,4-dimethyl-substituted 8-oxabicyclic ring system. Syntheses of α,β-epoxy-N-aziridinylimines, known precursors to α-hydroxyalkylidene carbenes, are achieved in 5-6 steps through initial stereoselective addition of a vinyl lithium species to 2,4-dimethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one. The diastereoselectivity (diastereotopic group selectivity) of the alkylidene carbene insertion reaction is reversed upon protection of a tertiary alcohol at C-3 of the oxabicylic ring system as a trimethylsilyl ether. Application of the hydroxycyclopentene annulation on an 8-oxabicyclic ring system bearing a benzyloxy substituent on the 2-position is described in chapter 3. Selective insertion adjacent to the benzyloxy group is observed irrespective of the tertiary alcohol substituent at C-3. Competing O-H and O-Si insertion, fragmentation and 1,2-rerrangement occur to a much greater extent than for the 2,4-dimethyl system. Chapter 4 compares the selectivity of alkylidene carbenes generated in the dimethyl and benzyloxy-substituted oxabicyclic ring systems. Alkylidene carbenes lacking the α-hydroxy group, generated via either the deprotonation of vinyl chlorides, or the reaction of ketones with lithio(trimethylsilyl)diazomethane, show similar reactivity differences in the 3-trimethylsilyloxyoxabicyclic systems as those bearing the α-hydroxyl group. The ratio of C-H insertion to O-Si insertion depends on the method of generation employed.