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Regenerable thiophenolic radical-trapping antioxidants
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
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2015 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 24, 6162-6165 p.Article in journal (Refereed) Published
Abstract [en]

Diphenyl disulfides carrying alkyltelluro groups in the o-, m-, and p-positions were prepared using ortho-lithiation and lithium halogen exchange reactions. The novel antioxidants showed only minimal inhibitory effect on the azo-initiated peroxidation of linoleic acid in chlorobenzene until reduced to the corresponding thiophenols by tris(2-carboxyethyl)phosphine (TCEP). The best in situ generated thiophenol (from 7c) under these conditions quenched peroxyl radicals more efficiently than α-tocopherol with an almost 3-fold increase in inhibition time.

Place, publisher, year, edition, pages
2015. Vol. 17, no 24, 6162-6165 p.
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-269896DOI: 10.1021/acs.orglett.5b03169ISI: 000366878300057OAI: oai:DiVA.org:uu-269896DiVA: diva2:885408
Funder
Swedish Research Council, 621-2011-4006Carl Tryggers foundation , CTS:120
Available from: 2015-12-18 Created: 2015-12-18 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Regenerable Organochalcogen Antioxidants: An Explorative Study
Open this publication in new window or tab >>Regenerable Organochalcogen Antioxidants: An Explorative Study
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Antioxidants are widely used to protect organic materials from damages caused by autoxidation, an oxidation process that occurs under normal aerobic conditions. In this thesis, novel multifunctional organoselenium and organotellurium antioxidants were designed, synthesized, and evaluated in search for compounds with better radical-trapping capacity, regenerability, and hydroperoxide-decomposing ability.

Selenium was incorporated into ebselenols and hydroxy-2,3-dihydrobenzo[b]selenophenes and tellurium into diaryl disulfides and aryltellurophenols. All newly developed antioxidants were evaluated in a chlorobenzene/water two-phase lipid peroxidation system containing suitable co-antioxidants in the aqueous phase. Ebselenol carrying a hydroxyl group (OH) ortho to selenium showed a two-fold longer inhibition time than the reference α-tocopherol in the presence of aqueous-phase ascorbic acid. 2,3-Dihydrobenzo[b]selenophenes carrying a 5- or 7-OH outperformed α-tocopherol both when it comes to radical-trapping capacity and regenerability. Alkyltellurothiophenols, in situ formed from their corresponding disulfides by tris(2-carboxyethyl)phosphine, were also efficient regenerable radical-trapping antioxidants. The consumption of N-acetylcysteine in the water phase was followed and found to be limiting for the duration of the inhibition. The hydroperoxide-decomposing ability of all organoselenium antioxidants was evaluated. Ebselenols were often better glutathione peroxidase mimics than the parent.

In an effort to find out more about antioxidant mechanisms, aryltellurophenols carrying electron donating and electron withdrawing groups in the phenolic or aryltelluro parts were synthesized and OH bond dissociation enthalpies, BDEO-Hs, were calculated. Compounds carrying electron donating groups in the phenolic or aryltelluro part of the molecule showed the best radical-trapping capacity. Deuterium labelling experiments suggested that hydrogen atom transfer could be the rate-limiting step in the antioxidant mechanism.  

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1556
Keyword
autoxidation, antioxidant, selenium, tellurium, regenerable, multifunctional, radical-trapping, hydroperoxide-decomposing, co-antioxidant
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-329217 (URN)978-91-513-0068-9 (ISBN)
Public defence
2017-10-27, B7:101a, BMC, Husargatan 3, 751 23, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2017-10-05 Created: 2017-09-10 Last updated: 2017-10-18

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Yan, JiajiePoon, Jia-feiSingh, Vijay PEngman, Lars

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