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Gewählte Master / Diploma Thesis:

Erika Schaudy (2017): SYNTHESIS OF NATURAL ANTIOXIDANTS.
Master / Diploma Thesis - Abteilung für Chemie nachwachsender Rohstoffe, BOKU-Universität für Bodenkultur, pp 90. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
Various reactions in nature cause formation of free radicals and reactive oxygen species. They accomplish essential functions in cells, whilst their accumulation might effect unwanted chemical modifications of cellular constituents. Specific molecules, termed antioxidants, are able to react with these compounds and prevent oxidative damage. The antioxidant hydroxytyrosol, (3,4-dihydroxyphenyl)-ethanol, represents one of the most potent scavengers of free radicals in nature, which explains the continuing interest in this compound, e.g. in food and cosmetics industries. Extraction and purification from olive fruits, as the main source, is a laborious process and yields the target compound in low yield, thereby raising its price. To cover the demand for future applications at a reasonable price, alternative production ways are sought for. The present thesis aimed at a new production route towards hydroxytyrosol, combining the whole-cell biotransformation of aryl halides to the respective catechols, catalysed by the recombinantly expressed enzymes toluene dioxygenase and cis-toluene dihydrodiol dehydrogenase in E. coli JM109 (pDTG602), as initial step, followed by chemical modification of the product’s side chain. Bromo-2-iodobenzene, bromo-3-iodobenzene, chloro-2-iodobenzene and chloro-3-iodobenzene served as test substrates in the biotransformation. In the experimental setting, none of these compounds was significantly biotransformed. Bromobenzene, a compound already known to be a substrate, resulted in low yield of 3-bromocatechol in the same experimental setting, most likely due to suboptimal protein expression. A successful chemical synthesis route comprising five steps (acetylation of hydroxyl groups, Sonogashira-coupling reaction and selective cleavage of the protective group, anti-Markovnikov reductive hydration and deprotection of the hydroxyl groups) was established starting from commercially available 4-bromocatechol, yielding hydroxytyrosol in an overall yield of 21%.

Beurteilende(r): Rosenau Thomas
1.Mitwirkender: Hettegger Hubert

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