There is enormous interest in the design and development of efficient chiral ligands for asymmetric catalysis, as a result, this field has become one of the most popular areas of research in organic chemistry. This project involved the investigation of the novel chiral pentacyclo-undecane (PCU) diol 54a, PCU bisimine 87 and PCU bis(oxazoline) 100 type ligands. The PCU diol ligand was synthesized, but proved to be difficult to obtain enantiomerically pure which hindered further investigation into this type of ligand. The PCU bisimine ligand 87 was synthesized. However due to its instability it was not further pursued. Synthesis of the PCU bis(oxazoline) ligand 100 was successful. This ligand was complexed to various metal salts and its efficiency as a chiral Lewis acid catalyst was evaluated on the asymmetric Diels-Alder reaction between 3-acryloyloxazolidin- 2-one 52 and cyclopentadiene 33. The anhydrous magnesium perchlorate ligand complex emerged as the best catalyst providing the endo-cycloadduct product 53 in 81 % enantiomeric excess at -40 oC. Optimizations of the possible conformations of the magnesium complex of ligand 100 with the substrate 52 were performed using Density Functional Theory (DFT) calculations. The more energetically favoured complex conformation was established. The Re-face of the dienophile which was less hindered produced the product consistent with the experimentally observed product 16. Based on the calculated bond lengths from the computational model binding of the ether oxygen on the PCU moiety to magnesium was observed. All the novel compounds were fully characterized using NMR, IR and mass spectroscopy as the main tools. / Thesis (M.Sc.) - University of KwaZulu-Natal, Westville, 2008.

This work is an account of the extractives from one member of the Meliaceae and one member of the Ptaeroxylaceae. In all, thirteen compounds have been isolated, of which four have not been described previously. Neobeguea mahafalensis belongs to the Neobeguea genus and has been classified into the Swietenieae subfamily of the Meliaceae. Neobeguea mahafalensis seeds obtained from Madagascar were investigated for the presence of limonoids. This is the first time extracts of the seeds were investigated. Previous work was done on the stem bark of this species. An andirobin-type limonoid, methyl angolensate (5), two mexicanolide-type limonoids, mexicanolide (6), khayasin (7), and three protolimonoids, sapelin E acetate (8), sapelin C (9) and grandifoliolenone (10), have been isolated in this work. One of these was novel. Cedrelopsis grevei belongs to the Cedrelopsis genus and has been classified into the Ptaeroxylaceae family. Extracts from the stem bark of Cedrelopsis grevei obtained from Madagascar yielded seven compounds, a triterpenoid, β-amyrin (15), a coumarin, scoparone (16), a limonoid, cedmiline (14), a triterpenoid derivative, cedashnine (17), a quassinoid, cedphiline (19), a lignan, cedpetine (18) as well as sitosteryl β-D-glucopyranoside (20). Three of these were novel. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

Cage compounds have attracted pharmaceutical and biological interest amongst others as anti-Parkinson agents. The serendipitous observation of the activity of 1-aminoadamantane 1 in Parkinsonian patients against selected viruses i.e. Herpes simplex Type I & II and Influenza A2-Asian viruses/Taiwan has increased the interest in cage compounds. This study involves the synthesis of the cage amino acid 14. Due to the insolubility of pentacyclo-[6.3.0.02,6.03,10.05,9]-undecane (trishomocubane) amino acid 14 in both polar and nonpolar solvents, including DMSO (d6), the synthesis of Fmoc-tris amino acid 50 was required for analysis. The Fmoc derivative of trishomocubane amino acid was also useful for controlled* coupling of the cage amino acid 14 to short peptides. The synthesis of the Fmoc-tris amino acid fluoride derivative is described as well as that of the tri-peptide (Ala-Ala-Ala). The incorporation of the Fmoc-tris amino acid fluoride in a tetra-peptide Ala-Ala-Ala-tris and in a hepta-peptide Ala-Ala-Ala-tris-Ala-Ala-Ala will also be presented. A computational chemistry project was undertaken using density functional theory (B3LYP) at the 6-31+G(d) level of theory, so as to enhance the understanding of the mechanism of esterification. Methanol, acetyl chloride and acetic acid were used in the model for simplicity. Four membered ring transition states were obtained with both acetyl chloride and acetic acid. A six membered ring transition state is facilitated by the selective use of one methanol molecule from the solvent. Both a concerted and step-wise mechanism are presented. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2006.

The total mineral ion concentration of Rooibos Tea was determined using ICP-OES. Significant concentrations of Na, K, Mg, Ca, P were found, and trace levels of Al, Fe, Mo, Sr, Zn, Ba, Cu and Pb detected. Protocatechuic acid, aspalathin and rutin were identified in Rooibos tea infusions analysed with HPLC. Analysis of tea samples by Ion Chromatography showed the presence of Cr and S042- ions. Rooibos Tea liquor had a pH of 4.6 once equilibrium had been reached. Partition coefficients (1.0 - 1.4 mm sieving fraction) for Na+, K+, Mg2+, protocatechuic acid, aspalathin, rutin, S042- and Cl were determined for infusions at 80 C using a graphical and a successive extraction method. A total mineral content method was also used to determine the partition coefficients for the mineral ions. The Na+, K+, Mg2+,SO42-, H2P04- (as P) and Cl ions as well as protocatechuic acid, aspalathin and rutin all displayed first order behavior, allowing the determination of infusion rate constants. The particle size effect was investigated at 80 C. All the mineral ions showed an increase in infusion rate constant with decreasing particle size, protocatechuic acid and aspalathin showed no trend, while the rutin infusion rate constant was independent of particle size. Calcium uptake by the leaf was observed, this was more pronounced with the smaller particle sizes. Infusion rate constants and hence diffusion coefficients were determined for the nine species for temperatures ranging from 45 to 90 C. These diffusion coefficients for the mineral ions were compared with those for the respective species in aqueous media to give hindrance factors, which were of the order of 102. Except for Cl, all hindrance factors increased with an increase in temperature. The infusion rate constants for all the species at the various temperatures were fitted to an Arrhenius equation and activation energies of infusion determined. The values were lower than those predicted theoretically. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998

A comparative study was undertaken of different extraction methods for the isolation of volatile organic compounds from Murraya koenigii (curry leaf plant). The techniques studied included the traditional methods of extraction, namely, Soxhlet and solvent extraction as well as steam distillation. The solvent–free extraction techniques of headspace analysis and headspace solid phase micro-extraction (HS-SPME) were also investigated. In the evaluation of SPME, two different fibre coatings, poly(dimethylsiloxane) and poly(acrylate), were compared. Preliminary work to determine the effect of extraction parameters, such as extraction time, was carried out. The volatile oils in the fresh leaves of Murraya koenigii were isolated by the above-mentioned extraction methods and analysed by gas chromatography-mass spectrometry. The main aroma contributing compounds were identified by comparison of their retention times with those of standards and their mass spectra with those of known compounds contained in the National Institute of Science and Technology Standard Reference Database 1A (NIST 98). The essential oil contained mainly terpenes: monoterpene and sesquiterpene hydrocarbons. The constituents were identified and only the five selected analytes of interest, a-pinene, β-pinene, a-phellandrene, β-caryophyllene and a-caryophyllene were quantified in three of the methods, namely solvent extraction, soxhlet extraction and steam distillation. From the quantitative determination of the compounds of interest, steam distillation favoured the extraction of β-caryophyllene. The solvent and Soxhlet extractions showed no significant differences between the quantities obtained for a- and β- caryophyllene. The steam distillation and Soxhlet methods showed similar quantities of a-caryophyllene extracted. The extraction of the monoterpenes, a-pinene, β-pinene, and a-phellandrene, was favoured by the Soxhlet method of extraction. Quantification was difficult with HS-SPME and headspace analysis. Headspace analysis proved effective in the detection of the very volatile analytes. Headspace-SPME combined with GC-MS was found to be suitable for the identification of both monoterpenes and sesquiterpenes of M. koenigii. From this study, solvent extraction and Soxhlet extraction were found to be superior to the other methods studied for the characterisation and quantitation of the volatile organic compounds in essential oils of Murraya koenigii. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Several tetrahydroisoquinoline (TIQ) diamine derivatives were prepared for use as ligands in asymmetric transfer hydrogenation (ATH) of acetophenone of which 17 intermediates and the eight target ligands were novel compounds. The initial design followed that of Noyori, who presented the efficiency of his monotosylated diamine in ATH. A series of eight novel secondary amine derivatives (78a-g and 88) were prepared with substituents that influenced the electronics and the sterics of and around the nitrogen donor. Ligand 71 was shown to have no activity for the ATH of acetophenone. It was apparent from experimental observations that a balance between the electronic and steric characteristics of the substituent was necessary to facilitate activity. It was found that ligand 78d possessing a benzyl group, had the greatest activity (81 % conv.). The greatest selectivity was obtained with ligand 78f (77 % ee) having a chiral phenylmethyl substituent. It was discovered in the case of the active diamine ligands that an optimised 1500 equivalents of water was required in order to demonstrate any enantioselectivity. The exact role of the water has never been ascertained, although there are many publications in which the effect of water has been examined. The most active metal precursor was also investigated and [RhCl2(Cp*)]2 was found to be the best for these TIQ diamine ligands in the specified model reactions. This work has recently been accepted for publication and has established criteria for further rational design on this system. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

The replacement of copperlbrass radiators in the automotive industry with radiators made from aluminium components provided the basis of this research. Since aluminium is more susceptible to corrosion than either copper or brass, factors that contribute to its corrosion are of major interest and importance, and have been investigated. Three different aluminium alloys were selected for study because of a special interest in their corrosive behaviour by the automotive industry. These are the aluminium alloy AA 3003 (samples A and B) and two supplier specific alloys (sample D containing Zn and sample E containing Cu and Mg). The various joining operations used in the automotive manufacturing process dictated the preparation of the aluminium alloys used for corrosion studies. Mechanically Assembled (MA) aluminium radiators use alloy samples as supplied by the aluminium industry and hence suitable experiments were carried out on the 'as-supplied' (AS) samples used for both finstock and tubestock material. The development of Composite Deposition (CD) Technology to braze together finstock and tubestock material introduced new challenges to corrosion research. To gain an insight into the corrosion of a Brazed aluminium radiator, all samples were subjected to a thermal profile identical to that experienced industrially under a Controlled Atmosphere Brazing (CAB) furnace. Two cases of interest emerged. Firstly the 'heat-treated' (HT) samples were used to evaluate the effect ofheat treatment on the alloy's resistance to corrosion. Secondly, alloy samples treated with a Composite Powder Coating (CPC) and then subjected to the thermal profile provided a surface of an AI-Si melt which represented the brazed joint. Experiments on these samples yielded information on the AI-Si melt and the likely corrosion in a brazed joint. The resulting corrosion of the AS, HT and CPC samples immersed in various corrosive electrolyte solutions for 60 minutes was examined using two microscopic techniques. Firstly, the actual surface pitting was examined using a Scanning Electron Microscope (SEM), and secondly, cross-sections of the samples mounted in a resin, then suitably polished and etched were examined using an optical microscope to further reveal the nature of corrosion of the samples. The nature of corrosion was best revealed in an acidified chloride solution. The AS samples showed delocalised crystallographic pitting consisting of coalesced pits at localised regions of the surface. The HT samples showed IV localised crystallographic pIttIng consIstIng of many individual pits and intergranular corrosion both at and below the surface. Intergranular corrosion was most severe for HT sample E containing Cu and Mg. The CPC samples showed total corrosion of the surface layer and eutectic AI-Si melt, some crystallographic pitting of the a-AI filler metal, and crystallographic pitting including intergranular corrosion of the base alloy. The extent of corrosion was found to depend on the chemical composition of the aluminium alloys, the presence of Zn, Cu and Mg causing more severe corrosion of the aluminium alloys, with the effect ofZn being most severe. The electrochemical investigation involved the measurement of two fundamentally important parameters. Firstly, the open circuit potentials (OCP) of the alloy samples immersed in the various corrosive electrolyte solutions were measured as a function of time. Secondly, the pitting potentials (Bp) of the alloy samples were measured using anodic polarisation techniques by extrapolation of the resulting log i vs E plots. The OCP and Bp of the AS samples were found to be influenced by the chemical composition of the aluminium alloys. Heat treatment of the AS samples was found to change their microstructure and solid solution composition which in turn affected the electrochemical results. The effect of the Composite melt layer on the electrochemistry of the CPC samples is discussed. Micrographic and electrochemical results were used to assess the best combination of finstock and tubestock material that would yield an aluminium radiator most resistant to corrosion. The likely corrosion of the components in these combinations was assessed and these results were compared with the actual results obtained industrially using the SWAAT exposure test. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.

Ultraviolet irradiation of DNA induces the formation of a number of mutagenic lesions. The most prolific of these is the cis-syn thymine dimer (formed maximally at 260 nm) and this has been implicated in the reaction pathways that lead to ultraviolet-induced carcinogenesis. In order that the molecular events underlying these neoplastic events be understood, it is imperative that the thymine dimers formed in ultraviolet-irradiated thymine containing systems be quantitated. In this laboratory, dimer quantitation is performed using reverse phase high performance liquid chromatography (HPLC) with ultraviolet (DV) detection and the data obtained has allowed a kinetic mechanism for lesion formation to be proposed. Such studies have used in vitro thymine containing substrates (aqueous thymine, thymidine, thymidylyl-3',5'thymidine, calf thymus DNA and pUC19 plasmid DNA) to generate the thymine dimer using DV irradiation. with the planned extension of this research to in vivo cellular systems (where DNA and hence thymine concentrations are intrinsically less than those of in vitro systems), a more sensitive technique for thymine dimer quantitation is required. An immunological approach to providing this technique was chosen. Here, DV-irradiated DNA was injected into rabbits whose immune system mounted a ' response (i.e. antibody production) to the DV-DNA antigen. Blood was drawn from the rabbits at regular intervals to obtain the antibodies. The technique of immunoblotting was chosen and developed to allow detection of the thymine dimer antigen. This involved the reaction between the UV-DNA antigen, the primary antibody (generated by the rabbit) and a secondary antibody conjugated to an enzyme, all of which were immobilized on a commercially available membrane system. Detection and quantitation of the immune complex immobilized on the membrane was performed using the technique of enhanced chemiluminescence. Upon addition of a chemiluminescent substrate (luminol) to the immune complex, the horseradish peroxidase enzyme catalysed the reaction of luminol, with one of the products being light of 425 nm to 430 nm. This light impinged on a luminescence film which was developed and printed using standard photographic techniques. The use of dilutions of the primary antibody in the immunoblotting protocol with enhanced chemiluminescent detection, allowed correlations of antibody dilutions with UV-DNA antigen to be made. This immunoblotting technique with enhanced chemiluminescent detection has been used successfully in detecting thymine dimer lesion formation at levels currently above the detection limit of the HPLC. It has also been used successfully in detecting and quantitating thymine dimers at levels undetectable by the HPLC. To this end it has proved to be 4000 to 8000 times more sensitive than the chromatographic technique. Any immunological technique requires that the antibody of interest be purified and characterized. Here, purification of the crude serum was performed using the classical technique of ammonium sulphate precipitation of proteins. As an alternative technique, affinity chromatography was performed on the crude serum using a Memsep 1000 affinity chromatography cartridge attached to a preparative HPLC system. Chromatographic data illustrating this purification are given. Characterization of the DV-DNA antigen was performed by considering the specificity of the antibody response in the laboratory animal. Support for the kinetic mechanisms previously proposed for pyrimidine dimer formation in DNA is also given in this work. Calf thymus DNA was irradiated and dimer yields obtained by immunoblotting. These were used in the computer programme CAKE together with the previously determined rate constants to determine simulated dimer yields. A good agreement between experimental and simulated data indicated the validity of the mechanism at a DNA concentration of 0.025 mg/ml. / Thesis (M.Sc.)-University of Natal, Durban, 1992.

The experimental work described in this thesis is aimed at the elucidation of the speciation of the zinc and germanium 8-hydroxyquinoline systems. A knowledge of this speciation could aid in modelling the kinetics of solvent extraction of zinc and germanium with 7alkyl derivatives of 8-hydroxyquinoline. In this study the stability constants of the ligand 8hydroxyquinoline with the ions H+, Zn2+ and Ge4+ have been investigated by potentiometry at 25°C in a partially aqueous medium. A titration technique was used in which the hydrogen ion concentration was monitored using a glass indicating electrode. The partially aqueous medium comprised of O. 1 mol dm- 3 NaCl04 in 60% (v/v) dioxane and the concentration levels of the reagents were at least millimolar. The analysis of the potentiometric data was carried out with the aid of the computer programs HALTAFALL, ESTA and STATGRAPHICS. The results obtained for the systems involving the H+ and Zn2+ ions compare with those reported in the literature. The stability constant of a protonated species in the zinc-8-hydroxyquinoline system (ZnLH) was established for the first time. Precipitates obtained from the Zn2+ titrations were identified as zinc 8-hydroxyquinolate dihydrate. The germanium 8-hydroxyquinoline system has not been studied previously via potentiometry techniques. The complex hydrolysed species of germanium in aqueous solutions and the unusual features displayed in the formation curves increased the complexity of species selection. Although a suitable model of the species present could not be determined some evidence suggests the presence of protonated species. Hence, a prerequisite for resolving the germanium-8hydroxyquinoline system could be a more complete understanding of the hydrolysis of germanium in the partially aqueous medium used. / Thesis (M.Sc.)-University of Natal, Durban, 1991.

The aim of this investigation was to develop and test a theory that allowed for the calculation of the activity coefficients at infinite dilutions (l' ~ 3) from G.L.C. measurements using moderately volatile solvents. The solvents chosen for study were straight chained (Cs to C7) and cyclic (Cs, C6 and benzene) liquid hydrocarbons using cis- and trans-decahydronaphthalene (decalin) as the stationary liquid phase (solvent). The systems were studied at two different temperatures, 283.15 K and 298.15 K. The solutes were n-pentane~ n-hexane, n-heptane, cyclopentane, cyclohexane and benzene. This method for the determination of activity coefficients has the advantage of being able to work at infinite dilution, whereas in other techniques, extrapolation to infinite dilution of finite-concentration data is necessary. In addition solutes are separated from impurities when chromatographed so that only very small quantities of moderately pure material need be· used. However the technique is also limited since the solute studied (injected reagent) needs to be volatile, while the solvent (liquid stationary phase) should be involatile. The solvents chosen in this experiment (cis- and transdecalin) are moderately volatile which introduces many limitations since the theory developed for the determination of activity coefficients at infinite dilution is restricted to involatile solvents. However a novel method for working with moderately volatile solvents is developed by relating the loss of solvent to its partial pressure and modifying the existing theory. In the past the use of precolumns and/or saturators, coarse packing, small pressure gradients, and internal standards were used when working with volatile solvents. However employing this new method excludes the use of precolumns, saturators, or internal standards, and allows any type of packing and pressure gradient to be used. The calculated activity coefficients are compared with literature values, where the wor~ers employed G.L.C. techniques, and with predicted values. The activity coefficients calculated at both temperatures are used in the calculation of excess partial molar enthalpies. These results are compared with values obtained from finite concentration data by other workers. / Thesis (M.Sc.)-University of Natal, Durban, 1992.