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Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Attempts have been made to transform lanosterol, by both chemical and microbial means, into compounds of potential pharmacological importance. In part I some compounds with heterocyclic rings (pyrazoles, isoxazoles, and furazans) fused to ring-A have been synthesized by chemical methods. These have been tested for cytotoxic properties against lymphoid leukemia L-1210. The equilibria and n.m.r. spectra of some formyl ketones have also been studied. In part II attempts have been made to oxidize some lanosterol derivatives with microbial cultures in pursuit of synthetically useful intermediates. 3β-Hydroxy-11-keto-4, 4, 14α-trimethyl-5α-chol-8-enic acid methyl ester (35e) has been synthesized from lanosterol and transformed by Trichotecium roseum to a dihydroxy-5α-cholenic acid derivative. Extensive chemical transformations have been carried out on lanosterol to prepare substrates for microbial transformation. In particular a new efficient method for the mild degradation of the lanosterol side chain to a 17β-acetyl group has been developed.

This thesis investigated the formation of compositional gradients across 0.5 – 1 cm of porous silicon layers which had thicknesses of 2 – 10 μm. These compositional gradients were then characterised, and their potential use as vapour sensors was probed. Surface composition gradients have been reported on flat surfaces, but this is the first time that they have been reported on a three-dimensional material with controlled pore geometry. Chemical gradients have been generated across the surface of porous silicon by performing electrochemical attachment of organohalides with an asymmetric electrode arrangement, and by chemical hydrosilylation of alkenes in the presence of a diffusion gradient of diazonium salts across the porous silicon surface. Samples with electrochemical gradients of methyl, pentyl acetate, and decyl and using chemical hydrosilylation with gradients of undecanoic acid and decyl groups. The latter four gradient-modified porous silicon types have been ‘endcapped’ with methyl groups to give improved stability and greater hydrophobicity. The pentyl acetate and undecanoic groups have been converted into pentanol and undecanoate groups respectively to increase the hydrophilicity of these porous silicon surfaces. The gradients have been characterised using two-dimensional FTIR microspectrophotometry and water contact angle measurements. The interaction of these gradient porous silicon samples with ethanol, heptane, toluene and 2-hexanol vapours have been monitored either by UV-Vis reflectance spectroscopy at selected points across the surface or more globally using a digital camera. The undecanoate gradient porous silicon sample showed a large difference in optical response between the undecanoate end and the methyl end of the gradient when exposed to water vapour, showing that imposition of a chemical gradient can alter the sensing character of porous silicon in a controllable manner.

Picrotoxin is the bitter tasting convulsive poison, obtained from the cocculus berries, the fruit of the East Indian creepers, Menispermum cocculus and Anamirta paniculata. It has been used extensively in medicine as anti-barbiturate. Although picrotoxin was first isolated in 1812 by Boullay and has been the subject of exhaustive research since then, the problem of its structure is still incompletely solved.

2-Oxonanoyl oxide (27) has been converted to the 2-hydroxy ether (65) and the 2-oxo ether (66) both of which Possess ambergris-type odours similar to that of the odiferous compound (1). The route which affords the highest yield is via the intermediates (64), (75), (43) and (36), and this gives 23% of the 2-oxo ether (66) and 17% of the hydroxy ether (65) from 2-oxomanoyl oxide. A two-step transformation of manoyl oxide (26) into the Perfume (1) has been achieved by oxidising manoyl oxide with chromium trioxide in acetic acid, and then reducing the resulting lactone (55) directly to its cyclic ether (1). Attempts were made to synthesise new ambergris-type perfumes, and successful preparation of the internal ketal (108) showed that contrary to expectations this ketal is odourless. Comparison of the mass spectra of the lactones (54), (55), (56), and (145), with those of their c8 epimers (57), (58), (59), and (146) respectively, showed that the trans-fused lactones lose carbon dioxide upon electron-impact while the cis-fused isomers do not.

This thesis describes the chemical, physico-chemical and structural studies of two types of copper compounds which interact with molecular oxygen in their formation. The first type is an intensely coloured species based on the ligand oxalyldihydrazide. The divalent metal and the ligand react together with simple carbonyl compounds and molecular oxygen in basic conditions to form blue species the nature of which has been the subject of conjecture for many years. This work shows that the metal is trivalent in the highly coloured states and that it acts as an oxidative catalyst with ascorbic acid. The copper (III)/copper (II) potential has been established as +0.244V by polarography. Compounds including acetaldehyde and acetone as the carbonyl component have been crystallized in monoclinic space groups. In both instances X-ray diffraction studies show that the metal is co-ordinated to a 6-5-6-5 macrocycle formed by a condensation reaction between two oxalyldihydrazide molecules and two carbonyl moieties. The co-ordination is via four deprotonated 'amide' nitrogen atoms and is of square-planar geometry. A structural study of oxalyldihydrazide has also been undertaken and comparisons are made with the co-ordinated species. The second type of compound studied is a Cu4OX6L4 cluster. It was made from a copper(I) precursor and studies with oxygen-18 gas show that formation requires oxidation to copper(II) followed by hydrolysis. Infrared evidence based on the Cu-O stretch (500-580 cm-1) is presented. Attempts to include both fluorine and iodine as the halogen component suggest that only chlorine and bromine may fill such a role.