Preparation and Antitumour Studies of Some Ruthenium and Iron Cyclopentadienyl Complexes

Abstract

In this work, a series of mono-, di-and pentasubstituted metallocene compounds of iron and ruthenium was prepared, with all compounds screened for their antitumour properties. Chapter 1 includes a review of the use of metals in medicine, in particular, their application to the treatment of cancer. Metal-containing compounds have been shown to possess great potential as antitumour agents, as evidenced by their current medical use and their significance in recent literature. In Chapter 2 the synthesis of a key starting material and its conversion to a large number of pentasubstituted ruthenocenes is discussed. The pentamethyl ester (1) was prepared by a modified literature method, which involved a reduction in the number of steps and the substitution of a thallium reagent for silver. On one occasion the unusual ruthenocene derivative Ru[?5-C5H4(C5(CO2CH3)5)][?5-C5(CO2CH3)5] (2) was isolated from the reaction mixture of (1). Attempts to prepare (2) by rational routes were unsuccessful. A potassium salt of ruthenocene pentacarboxylic acid was prepared using base catalysed hydrolysis of (1), while acid hydrolysis of (1) produced ruthenocene pentacarboxylic acid (6). A series of new pentasubstituted alkyl esters was produced using (6), with the general formula Ru(?5-C5H5)[?5-C5(CO2R)5]. All of these new esters were found to be oils, with the exception of the iso-propyl ester which is a waxy solid. Similarly, the synthesis of a small number of new pentasubstituted amides was achieved from (1). The pentafluorocarbonyl ruthenocene (9) was synthesised from (6) and proved to be a useful reagent for the synthesis of a number of new pentasubstituted ruthenocenes. The pentamethylcyclopentadienyl analogue of (1) was converted to the carboxylic acid and the n-propyl ester via acid catalysed hydrolysis and esterification. Synthesis of the mono-and dicarboxylic acid and fluorocarbonyl ruthenocenes gave way to the production of a range of mono-and disubstituted ruthenocene carbonyl compounds. These compounds include methyl, ethyl and propyl esters, the propyl thiocarbonyl compound, glycoconjugate compound and ethanolamides of ruthenocene. The anhydride (10) was found to be a by-product of the synthesis of the mono-and difluorocarbonyl compounds but was later able to be prepared rationally. As well as these ruthenocenes, the ferrocene mono-and di-methyl and propyl esters were prepared for later biological testing. Mono-and di-alkyl and ketone ruthenocenes, and the previously known formyl ruthenocene were prepared using methods adapted from the literature. A cationic mixed ruthenocene was prepared using two different methods, and completely characterised. All of the compounds prepared were fully characterised, with crystal structures obtained for Ru[?5-C5H4(C5(CO2CH3)5)][?5-C5(CO2CH3)5], Ru(?5-C5H5)[?5-C5(CO2H)4(CO2K)], Ru(?5-C5H5)[?5-C5(CO2H)5], [Ru(?5-C5H5)(?5-C5H4CO)]2O, Ru(?5-C5H5)[?5-C5(CO2C6H5)5], Ru(?5-C5H5)[?5-C5(CONH(CH2)2CH3)5], Ru(?5-C5H5)[?5-C5(CONHC6H11)5]. Biological testing of all of the above compounds was performed against a range of tumour cell lines and a healthy cell line. This was done in order to establish whether the compounds were active against the tumour cells, whether the activity was selective towards the tumour cell lines, and to determine any structure-activity relationship among the compounds. SRB colorimetric cell survival assays were employed for this preliminary testing. While the potency of all of the compounds was found to be low, some selectivity towards the tumour cell lines was evident when compared to their activity against healthy NFF cells. Amongst the most active compounds was the pentapropyl ester (21) which presented an IC50 of 12 µM against the ovarian tumour cell line CI80-13S. As well as gauging their level of activity, a deeper understanding of the mode of action of the compounds was also sought. Ruthenium uptake measurements, cell cycle experiments and nucleotide binding studies were carried out in order to gain information about their mechanism. Since the compounds tested did not show similar activity to that of Cd2+, nor did they affect the cell cycle, it is uncertain whether the mechanism of action involves mitochondrial function. NMR nucleotide binding studies revealed a possible interaction between the tested compounds and 5'-GMP, however, further experiments are required to obtain an understanding of the mechanism of these compounds.