Show simple item record  

dc.contributor.advisorMain, Associate Professor Lyndsayen_NZ
dc.contributor.authorBrooks, Robert Turongoen_NZ
dc.date.accessioned2018-02-11T20:58:48Z
dc.date.available2018-02-11T20:58:48Z
dc.date.issued2009en_NZ
dc.identifierhttp://adt.waikato.ac.nz/uploads/adt-uow20100112.114659en_NZ
dc.identifier.citationBrooks, R. T. (2009). pH-sensitive Anticancer Model Prodrug: Amide of Kemp’s Acid (Thesis, Master of Science (MSc)). University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/11640en
dc.identifier.urihttps://hdl.handle.net/10289/11640
dc.description.abstractSolid tumours are characterised by lower extracellular pH (as low as 5.8 pH) compared to normal healthy cellular pH (actively regulated at pH 7.3). This difference may be exploited with an acid-sensitive anti-tumour prodrug which releases a cytotoxin selectively in tumour tissue. The research reported in this thesis was aimed at synthesising and performing rate studies on an amide prodrug with pH-sensitive rates of reaction in the pH 5 - 8 region. Amide hydrolysis is catalysed by neighbouring carboxylic acid groups in their fully protonated state but not in its ionised state (shown in the figure below), whereby pH sensitivity around pH 5 - 8 can be exploited. The current study was carried out on an amide of Kemp's acid which, due to enforced stereochemistry of carboxylic acid and amide functional groups, has the type of structure conducive to accelerated amide hydrolysis. The rates for tertiary and secondary aliphatic amides of this Kemp's acid system have shown high reactivity at low pH and a large reduction in rate across pH 5.8 - 7.3, however an aryl amide had not previously been studied. It was thought that an aryl amide of Kemp's acid would provide a faster rate of reaction compared with the alkyl amides, and also aryl amine cytotoxins exist which could be attached as an amide. A secondary aryl amide of Kemp's acid (58) was obtained via a potassium hydroxide ring-opening reaction on a synthesised imide of Kemp's acid (43). Aliquots of the ring-opened amide (58) were added to buffered (phosphate and malonate) aqueous solutions (with ionic strength μ = 1 mol L-1) and the hydrolysis reaction followed at 30.0 oC across the pH range 0.48 - 8. First order rate constants were calculated from absorbance change with time and the pH-rate profile established. Absorbance changes were shown to be consistent with amide hydrolysis with no evidence of any imide reformation as evident in other studies. The rate data were analysed. There was no evidence from rates for the two successive acid ionisations with only a single rate plateau evident from pH 2 to 5, suggesting that both ONHCOOHCOO-OMe(58) iv di- and mono-acid species have very similar hydrolysis rates or that the second ionisation is low due to stabilisation of the mono-ionised molecule by hydrogen bonding interactions. For this reason, the rate profile could be analysed only as if it were a single ionisation in the same way that Menger and Ladika analysed their aliphatic tertiary pyrrolidyl amide in an earlier study. This analysis gave a pKa value of 6.72 0.09 and a limiting rate constant of 7.1 x 10-5 s-1. The studies revealed a three fold rate differential between pH 5.8 (faster) versus 7.3 (slower), a difference which is probably too small a selectivity for possible prodrug application. Separately, the second order rate coefficient for the reaction of potassium hydroxide solution to open the imide was also established (k2 = 0.00067 L mol-1 s-1 at 30.0 oC, μ = 1.00 mol L-1 with KCl).en_NZ
dc.format.mimetypeapplication/pdf
dc.languageenen_NZ
dc.publisherThe University of Waikatoen_NZ
dc.rightshttp://www.waikato.ac.nz/copyright.shtmlen_NZ
dc.rightsAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectAnticancer Model prodrugen_NZ
dc.subjectAmide Hydrolysisen_NZ
dc.subjectKemp's aciden_NZ
dc.titlepH-sensitive Anticancer Model Prodrug: Amide of Kemp's Aciden_NZ
dc.typeThesisen_NZ
thesis.degree.disciplineChemistryen_NZ
thesis.degree.grantorUniversity of Waikatoen_NZ
thesis.degree.levelMastersen_NZ
thesis.degree.nameMaster of Science (MSc)en_NZ
uow.date.accession2010-01-12en_NZ
pubs.place-of-publicationHamilton, New Zealand


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record