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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Bis-benzyl dianions were prepared from the three symmetrical dimethylbiphenyls in yields of 79-86%, and shown to react with a variety of electrophiles on the benzylic carbons. Electrophiles included dimethyl and diethyl sulfate, isopropyl bromide, t-butyl iodide, allyl chloride, trimethylsilyl chloride, trimethylgermyl bromide, and trimethyltin chloride. Reaction of the dianions with (alpha),(omega)-dihalides provides an excellent route to n.0 - and n.0.n.0 cyclophanes. An X-ray study on 14.0 paracyclophane showed it to have a conformation different from that observed in solution by NMR; MM2 calculations were used in determining what the solution conformation is likely to be. Oxidation of the dianions produced the monomer dihydrophenanthrene from the ortho isomer, dimer 2.0.2.0 metacyclophane from the meta isomer, and polymer from the para isomer. An X-ray study on 2.0.2.0 metacyclophane showed it to have the same conformation in the crystal as is observed in solution by NMR. An NMR method for determining the angle of twist in a biphenyl based on the chemical shift of the ortho hydrogens was developed. Many oxidizing agents were evaluated for the oxidation of the dianion from 2,3-dimethyl-1,3-butadiene to 1,2,5,6-tetramethylenecyclooctane; cupric bromide was found to be the best.

In this study, synthetic routes to certain short acyl chain phospholipids were developed. Their inhibitory or substrate properties for phospholipase A₂ were then examined. An improved method for the acylation of glycerophosphocholine is described using a mixed fatty acid - trifluoroacetic acid anhydride. This partial synthetic route is particularly suitable for obtaining short acyl chain phosphatidylcholines. A new pathway for constructing the unnatural sn-1-phosphatidylcholines is also described, starting from L-arabinose. This is converted first to a key intermediate, 2,3-O-isopropylidene-sn-glycerol, which is then phosphorylated and transformed into sn-glycero-1-phosphocholine. This can be acylated as above to give sn-1-phosphatidylcholines. Routes to the short chain phosphatidylethanolamines were investigated and discussed. A procedure, using phospholipase D, was used to convert L-diC₆ PC into L-diC₆ PE in a transphosphatidylation reaction. Failed attempts to obtain shorter chain homologs by this and other methods are also detailed. The kinetics of inhibition of the phospholipase A₂ hydrolysis of L-diC₆ PC by the D-isomer are also reported for the monomeric concentration range. It was found that the D- enantiomer did not behave as a pure competitive inhibitor, and that an enzyme-substrate-inhibitor complex can exist. The implications of these results with regard to PLA₂ hydrolysis of mixed micelles is discussed. The PLA₂ substrate properties of both the anionic and zwitterionic diC₆ PE's were also studied. It was established that the anionic diC₆ PE is either a very poor substrate relative to the zwitterionic diC₆ PE, or acts as a competitive inhibitor towards its hydrolysis. Similarly, the rates of base-catalyzed acyl ester hydrolysis are about 18 times greater for the zwitterionic than for the anionic diC₆ PE. The importance of a protonated amino group in both these hydrolyses studies is noted. In addition, certain physical properties of diC₆ PE, such as its critical micelle concentration and carbon-13 NMR spectrum, are also given.

Thesis (MTech(Chemistry))--Cape Technikon, Cape Town, 2001 / Many naturally occurring antibiotics have been identified and their synthesis successfully carried out in laboratories. It was envisaged by our group that by preparing a variety of, for example, quinoid compounds and then comparing their biological properties and activities, a better insight would be gained into a molecular structure - activity relationship. Chapter 1 deals with the attempted synthesis of 2-(1 '-hydroxyethyl)-3-(prop-2'enyl)- 1,4-benzoquinone (17) which may be converted by known methods into benzopyran derivatives. The second chapter describes a synthetic route to (±)(3R, 4R)-3,4-dihydro-3methyl- 4-hydroxy-l H-benzo[c]pyran-5,8-dione (42) and its (±)(45) diastereomer (43), both of which were found to be active against Gram negative and Gram positive organisms. The trans-l,3-dimethyl-4-hydroxypyranquinones (45) and (46) were also successfully synthesised. A different route of synthesis for the compounds (53), (54), (55) and (56) was also investigated. Several compounds were evaluated for biological activity. It was found that the quinones synthesised during this study were active against Gram negative and Gram positive bacteria, with the exception of compound (25) which had an acetate group in place of a hydroxy group. It was found that this trend was carried through all of the quinone derivatives tested.

by Chi-Duen Poon. / Bibliography: leaves 47-51 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

by Yu Li. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 97-104). / Acknowledgements --- p.i / Content --- p.ii / List of Schemes --- p.iii / List of Tables and Figures --- p.v / List of Spectra --- p.vi / Abstract --- p.ix / Chapter I. --- Introduction --- p.1 / Chapter I.1. --- The Conventional Ramberg-Backlund Reaction --- p.2 / Chapter I.2. --- The Meyers' Modification of the Ramberg-Backiund Reaction --- p.10 / Chapter II. --- The Evolution of a New Version of the Ramberg-Backiund Reaction: The Development of the Reagent KOH/A12O3- t-BuOH-CBr2F2 --- p.20 / Chapter III. --- Synthetic Applications of the New Version of the Ramberg- Backiund Reaction --- p.31 / Chapter III.1. --- "The Formation of Alkenes from α,α'-Hydrogen-containing Sulfones by Treatment with KOH/Al203-t-BuOH-CBr2F2" --- p.31 / Chapter III.2. --- Synthesis of (±)-Muscone from [12]Metacyclophane --- p.44 / Chapter III.3. --- A Non-pyrolytic Route to Corannulene --- p.49 / Chapter IV. --- Conclusion --- p.61 / Chapter V. --- Experimental --- p.62 / Chapter VI. --- References --- p.97 / Chapter VII. --- Spectra

Thesis (M.Sc.)--The Chinese University of Hong Kong. / Bibliography: leaves 90-96.

by Ho Kam Wah. / Thesis (M.Sc.)--The Chinese University of Hong Kong, 1973. / Bibliography: leaves 32-34. / Acknowledgements --- p.ii / Summary --- p.iii / Introduction --- p.1 / Synthetic Plans --- p.2 / Results and Discussion --- p.9 / Experimental --- p.22 / References --- p.32

Kuan Pui Kei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1979. / Bibliography: leaves 53-55.