No description available.

No description available.

No description available.

No description available.

The irnidazotetrazinones are a novel group of anti tumour agents which have demonstrated good activity against a range of murine tumours and human xenografts. They possess a structure activity relationship similar to the anti tumour triazenes, with the chloroethyl (mitozolomide) and methyl (temozolomide) analogues being active antitumour agents, whilst the ethyl (CCRG 82019) and higher homologues are inactive. This thesiS attempts to elucidate the biological mechanisms responsible for the strict structure-activity relationship observed amongst the imidazotetrazinones. Mitozolomide is the only agent chemically capable of cross-linking DNA , which has been suggested to be responsible fo r the cytotoxicity of this group of agents. Only mitozolomide and ternozolornide Exhibit a marked ditferential toxicity towards the 0 -alkylguanine-DNA alkyltransferase deficient GM892A (Mer-) cell line rather than the proficient Raji cell line (Mer+). The rate of uptake of imidazotetrazinones into cells is similar for all three agents in both cell lines, and does not explain the differing sensitivities to these agents. The effect of drug treatment on the incorporation of precursors into macromolecules, and their pool sizes, was examined. Temozolomide administration was found to alter de novo protein synthesis in both GM892A and Raji cells. Flow cytometric analysis revealed that temozolomide and CCRG 82019 block cells in late S/G2/M phase of the cell cycle , similar to that observed with mitozolomide. The extent of reaction of all three drugs with isolated macromolecules and cellular macromolecules was determined, and differences found, with cellular repair processes influencing the number of alkyl lesions remaining bound to macromolecules. The specific bases formed in calf thymus DNA after treatment with either temozolornide and CCRG 82019 was measured, and it was found that the types and relative amounts of lesions formed, differed, as well as the total level of alkylation. Whereas DNA extracted from imidazotetrazinone treated cells is not affected in its ability to support RNA polymerase activity, an effect is observed on the ability to extract DNA polymerase from drug treated cells. This may suggest that the alkylated DNA must be in intact chromatin for the lesion to manifest its effects. Temozolomide and methyl methanesulphonate do got appear to act with a synergistic mode of action. The 0 -position of guanine is suspected to be a critical site for the action of these types of drugs.

The use of Mitomycin C in the treatment of a wide range of neoplastic conditions is discussed. The mechanism of action of mitomycin anticancer antibiotics under reductive activation conditions using either enzymes, sodium dithionite, catalytic hydrogenation or chromium (Il) perchlorate is examined, as is the alkylation of DNA. An intramolecular [3+2] cycloaddition strategy has been employed to synthesise the pyrrolo[I,2-aJ]indole nucleus for a wide range of cyclopropamitosenes, whereas the key step in the synthesis of pyrrolo[I ,2-a]indoles without the cyclopropane ring was a modified Wittig reaction. From the onset of the work it was important to investigate the role of the 7 -methoxy group. Hence a variety of cyclopropamitosenes or related pyrrolo[I,2-a]indoles were subjected to C-7 exchange reactions with either (i) other alkoxides or (ii) cyclic / acyclic amines. In this way, structural modification at C-7 can be related to the biological results. Biological and electrochemical data were recorded for the cyclopropamitosenes and related pyrrolo[I,2-a]indoles and correlated with their structures.

No description available.

No description available.

No description available.

Mitomycin C (MMC), obtained from Streptomyces caespitosus, a clinically useful antitumour antibiotic, is the archetypical quinone bioreductive alkylating agent. The reductive activation mechanism of MMC, involves quinone reduction sequentially activating electrophilic sites in the drug molecule (C-l and C-lO for MMC). This research project was designed to investigate the role of the C-lO in alkylation processes by preparing compounds in which the electrophilicity at C-l is much reduced by substituting a cyclopropane for the aziridine ring. The resulting pyrrolo[I,2-a]indole, cyclopropamitosenes, could on reductive activation, by either 1- or 2-electron processes, followed by elimination of the carbamate, generate a powerful electrophile capable of alkylating DNA (or other nucleophiles) at C-lO .. A range of compounds was prepared utilising the azidocinnamate decomposition route to substituted indoles and an intramolecular [3 + 2] cycloaddition strategy was employed to synthesise the pyrrolo[I,2-a]indole nucleus. The rapid ring opening of cyclopropylcarbinyl radicals is briefly outlined. The reduction-initiated ring opening of the cyclopropane ring is investigated, thereby establishing its relevance to the potent bioreductive anticancer action of the cyclopropamitosenes, novel analogues of MMC. The design and synthesis of fused [I,2-a]indoles without the cyclopropane ring, is examined for comparative purposes. The key step in the synthesis is the formation of the [I,2-a ]indole nucleus via a radical cyclisation. Biological data were recorded for the cyclopropamitosenes and correlated with their structures.