Two different methodologies were used to attempt the synthesis of a novel P‐N ligand, denoted as PACNAC for the similarity to the analogous NACNAC and ACAC ligands. Although the synthesis of PACNAC was not successful, each methodology led to interesting discoveries. First, a number of lithium complexes of ketoimines were isolated and studied by Xray crystallography and NMR spectroscopy revealing some interesting substituent based effects on the structure, solubility and solution state behaviour. The X‐ray data of the two known and two related novel ketoimines were also collected and compared to the lithium complexes. Secondly, the synthesis of novel alkynyl imines along with the new alkynyl diimines by novel synthetic routes and studied by x‐ray crystallography, NMR, electrochemistry, and UV‐Visible spectra. / xvi, 134 leaves : ill. (some col.) ; 29 cm + 1 CD-ROM

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No description available.

The genus Helichrysum (Asteraceae) consists of approximately 500 species worldwide, with 245 indigenous to South Africa. As a result of the large number of species, the chemistry and biological activity of several species have not yet been investigated. The aim of this project was to investigate the phytochemistry of three species and propose a synthetic route to one of the antibacterial compounds isolated. An extensive literature review regarding the widespread traditional uses, biological activity and phytochemistry of the South African Helichrysum species is provided. From Helichrysum splendidum, a plant used traditionally to treat rheumatism, two monomeric guaianolides and a dimeric guaianolide, helisplendidilactone, were isolated. The stereochemistry of these known compounds was confirmed and the NMR assignments for certain peaks of helisplendidilactone were corrected. An X-ray structure for helisplendidilactone was obtained for the first time. The phytochemistry of Helichrysum montanum was investigated for the first time and new diastereoisomers of known guaianolides were isolated. The phytochemistry of H. splendidum and H. montanum is remarkably similar and supports their morphological classification in the same taxonomic group. The chloroform:methanol extract of H. montanum yielded a new dimeric guaianolide, 13’-epihelisplendidilactone, which is related to helisplendidilactone, as well as three monomeric guaianolides (of which one is a new diastereomer of a known compound). The extract also yielded spathulenol (a sesquiterpene), umbelliferone (a coumarin) and 4’,5,7-trihydroxy-3,3’,8-trimethoxyflavone (a flavonoid). Thirty-five Helichrysum species were screened for antimicrobial activity against six microorganisms and a preliminary cytotoxic assay, which included the use of “normal” and cancer cell lines, was performed. H. excisum was selected for further study based on the fact that it exhibited promising antimicrobial activity and relative low toxicity. Furthermore, with the exception of the essential oil, the phytochemistry of this species has not been investigated. From the aerial parts of H. excisum, five flavonoids, identified as pinocembrin, gnaphaliin, lepidissipyrone, 5-hydroxy-7,8-dimethoxyflavone and isoscutellarein 7-O-b-glucoside were isolated. Four of these flavonoids have an unsubstituted B-ring, a phenomenon often observed in flavonoids isolated from Helichrysum species. The active antimicrobial component of H. excisum has been identified as lepidissipyrone. Owing to the interesting biological activities reported for phloroglucinol a-pyrones and the synthetic challenges associated with these molecules, lepidissipyrone was selected for a synthetic study. Both the flavanone and pyrone moieties present in lepidissipyrone have been successfully synthesised. A successful strategy towards the CH2 linker between the two units has been illustrated. The strategy could be used to synthesise similar phloroglucinol-derived pyrones. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.

The total synthesis of a novel diarylheptanoid isolated from a South African medicinal plant, Siphonochilus aethiopicus, was investigated. S. aethiopicus (Indungulu in Zulu) is the only South African species of the Zingiberaceae plant family and is widely used in traditional medicine. One of the compounds isolated from this plant is a novel diarylheptanoid. Diarylheptanoids constitute a distinct group of natural plant metabolites characterized by two aromatic rings linked by a linear seven-carbon aliphatic chain, with varying functional groups on the aryl and the aliphatic chain. The target molecule for our synthesis contains two highly oxygenated aryl rings linked by an aliphatic chain with two stereogenic centres and a trans-alkene. In this study we present our investigation of different strategies to a viable synthetic method that could provide material to supplement the relatively small quantity of product that can be isolated from the plant extract. The major challenges of this synthesis were to develop procedures for the preparation of the homobenzylic trans-alkene, the stereogenic centres and to attach the electron-rich aromatic rings to the aliphatic chain. In this thesis the following aspects are described: • Various types of olefination reactions (including Wittig, Julia and organometalic-mediated type of olefination reactions) • Various types of alkylation reactions (including Grignard, Friedel-Crafts and organometalic-mediated type of alkylation reactions) • Incorporation of the stereogenic centres (including asymmetric hydroxylation and use of chiral starting materials) The synthesis will not only give a viable synthetic route to the target compound but is also versatile enough to allow the preparation of analogues. / Thesis (Ph.D. (School of Chemistry)) - University of KwaZulu-Natal, Pietermaritzburg, 2008.

Abstract available in pdf file.

The research undertaken in this thesis includes microwave-assisted extraction (MAE), synthesis, and the investigation of the scale-up of the microwave-assisted processes with the numerical aid. / The main goal of this research is to study the various problems associated with the scale-up of the microwave-assisted extraction and synthesis processes. Laboratory studies were carried out to investigate the microwave-assisted extraction of known components from peppermint leaves and American ginseng. Various factors that influence the extraction processes were studied. Microwave-assisted extraction method was compared with conventional heating and room temperature extraction methods on the extraction of ginsenosides from American ginseng. Microwave-assisted extraction method was determined to have higher extraction rate than both room temperature extraction and reflux temperature extraction using hotplate heating indicating that there is acceleration factor in enhancing the extraction rate beyond the temperature influence. / In the study of synthesizing n-butyl paraben, microwave-assisted synthesis was observed to greatly increase the yield of n-butyl paraben in much shorter period of time compared to the classic synthesis method. A transition state theory was proposed to explain this rate enhancement. The study of the synthesis of parabens with different alcohol and the influencing factors on the synthesis of n-butyl paraben yield were also studied. / A visualization method was developed to determine the microwave distribution in a domestic microwave cavity. The method uses gypsum plate as carrier and cobalt chloride as indictor. A simulation program was developed using the finite difference time domain (FDTD) approach and written in C programming language. The program was proved to be very versatile in different type of cavity simulation. Not only cavities with different dimensions and geometrical designs can be simulated, multiple magnetrons and various ways of magnetron placement can also be integrated into the simulation program. The detailed power distribution can be visualized in a 3-D plot, and the power distribution in each layer can be analyzed using the simulation result. The power distribution information will be very useful and necessary before any real equipment development.

Diquinoline molecules have been shown previously to have interesting inclusion properties. Of the nine new, targeted molecules produced for this work, seven formed inclusion compounds, and their solid-state structures are discussed herein. Chapter 2 shows the effect that substituting a hydrogen atom with a chlorine atom has on the inclusion properties. This comes about because of the additional intermolecular attractions that are now possible, and a wider range of guest molecules is included as a result. A new homochiral aromatic 'swivel offset face-face (OFF)' interaction is observed. Chapters 3 and 4 deal with the effect of adding extra aromatic planes to the target molecules, two or four planes, respectively. Each of these host molecules formed dimeric host-host units that are extremely similar across all crystal structures. These dimers mainly employed aromatic edgeface (EF) interactions. Chapter 5 looks at the effect of combining the modifications described in Chapters 2-4, namely additional aromatic surfaces and atom substitution. The resulting host molecule specifically includes polyhalomethane guests. In addition, this host molecule formed two concomitant pseudo-dimorph compounds with chloroform-d. The diquinoline host molecule presented in Chapter 6 incorporated an isomeric central linker ring to the other compounds. Although only a single crystal structure could be obtained, 1H NMR spectroscopy experiments show other small aromatics may be included. The effect of electron donating chemical substituents was examined in Chapter 7. These compounds were found to be quite insoluble, and did not produce crystals suitable for X-ray analysis. The host molecules in Chapter 8 contain electron withdrawing nitro groups. The two isomeric compounds that act as inclusion hosts show quite different properties. One of these hosts forms a series of inclusion compounds with water, in which the site occupancy of the guest can range from 0-100% without change to the overall structure. All the X-ray structures described have been analysed in crystal engineering terms, and their supramolecular interactions described in detail.

Includes copies of articles co-authored by the author during the preparation of this thesis. / Includes bibliographical references (leaves 334-376). / viii, 376 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Aims to increase understanding of the metabolism and disposition of methadone in humans, in particular in subjects receiving methadone maintenance treatment for opioid dependence, and to identify factors which may contribute to inter-subject variability in these processes, with respect to stereoselectivity / Thesis (Ph.D.)--Adelaide University, Dept. of Clinical and Experimental Pharmacology, 2001

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Ragauskas, Arthur; Committee Member: Bunz, Uwe; Committee Member: Cairney, John; Committee Member: Collard, David; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.