dc.description.abstract | Chapter 1; A literature review of chemotherapeutic agents, bioreductive prodrugs
and polycyclic diazoles, along with the aims and objects of the thesis is presented.
Chapter 2; A review of 'oxidative' homolytic aromatic substitutions carried out in
the presence of the 'reductant' Bu3SnH is presented. This is followed by the first
report of one-pot double intramolecular homolytic aromatic substitutions of alkyl
radicals onto heteroarenes. Bu3SnH / ACCN (1,1-azobis(cyclohexanecarbonitrile))
mediated double six-membered radical cyclizations using phenylselenides proceeded
in excellent yield to give dipyrido ring-fused imidazo[5,4-f]benzimidazole and
imidazo[4,5-f]benzimidazole. Optimized yields of 5 and 7-membered radical
cyclizations were obtained through ring activation with camphorsulfonic acid or
acetic anhydride. Annulated imidazobenzimidazoles were converted into
iminoquinone and quinone derivatives for anti-cancer studies.
Chapter 3; A review of oxidative cyclizations of ortho-substituted tertiary-anilines
is presented. A mechanism for oxidative cyclizations of o-tert-amino acetanilides to
give alicyclic ring-fused diazoles is proposed using the hydrogen-bonded amine-Noxide
intermediate (X-ray crystal structure provided). Oxone¿ in formic acid is
shown to give high yields of annulated benzimidazoles, as well as [1,4]oxazino ringfused,
and unsymmetrical pentacyclic imidazo[5,4-f]benzimidazoles. Imidazo[5,4-
f]benzimidazoles were converted into quinones, and an X-ray crystal structure of
[1,4]oxazino[4,3-a][1,4]oxazino[4',3':1,2]imidazo[5,4-f]benzimidazoliumquinone
di(trifluoroacetate) obtained.
Chapter 4; Cytotoxicity towards two human cancer cell lines known to over-express
NAD(P)H:quinone oxidoreductase 1 (NQO1), as well as a human normal fibroblast
cell line is presented. Increasing the alicyclic ring size or the degree of ring fusion,
resulted in decreased cytotoxicity, while the [1,4]-oxazino ring increased toxicity.
Mitomycin C (MMC) showed higher cytotoxicity than the synthesized compounds,
and computational docking of MMC into the active site of NQO1 revealed it to be a
better substrate for NQO1 than the synthesized compounds. Cytotoxicity testing
performed at the US National Cancer Institute using 60 human cancer cell lines
showed an iminoquinone to be particularly potent, with a good correlation to NQO1.
Chapter 5; All experimental detail is described for Chapter 2, 3 and 4. | en_US |