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Design principles for a-tocopherol analogues
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II. Organisk kemi.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II. Organisk kemi.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II. Organisk kemi.
2006 (English)In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 4, 846-852 p.Article in journal (Refereed) Published
Abstract [en]

An (RO)B3LYP/LANL2DZdp//B3LYP/LANL2DZ model for the prediction of the homolytic bond dissociation enthalpy (BDE) and adiabatic ionisation potential (IP) of phenolic antiocidants containing heavy chalcogens has been developed. The model has been used to probe the relationship between geometry, chalcogen substitution and activity for a series of a-tocopherol analogues of varying ring size. From this, a series of design principles for cyclic antioxidants has emerged, embodied by the compound 4-hydroxy-2,2,3,5,6-pentamethylbenzoselenete (4c). This compound is predicted to have a BDE comparable to a-tocopherol, and should act in a dual chain-breaking and hydroperoxide-decomposing manner, by analogy with other selenide antioxidants. The stability of chalcogen-substituted benzoxetes was considered, and the as yet unsynthesised benzotelluretes are predicted to be stable. Finally, an attempt was made to determine antioxidant mechanism by considering calculated BDE and IP data together with experimental rate data.

Place, publisher, year, edition, pages
2006. Vol. 4, 846-852 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-76069DOI: 10.1039/b515712aOAI: oai:DiVA.org:uu-76069DiVA: diva2:103980
Available from: 2007-02-28 Created: 2007-02-28 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Design, Synthesis and Evaluation of Catalytic Chalcogenide Antioxidants
Open this publication in new window or tab >>Design, Synthesis and Evaluation of Catalytic Chalcogenide Antioxidants
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the design, synthesis and evaluation of novel chalcogenide antioxidants.

A computational model for the prediction of antioxidant properties of chalcogen-containing antioxidants has been developed. The model has been used to probe the relationship between geometry, chalcogen substitution and activity for a series of α-tocopherol analogues of varying ring size and chalcogen substitution.

A series of simple diaryltellurides and aryl-alkyl tellurides have been synthesised. The selenium analogue of α-tocopherol has been synthesised in eleven steps and 6.5% total yield, with formation of the selenacycle by homolytic substitution at selenium as the key step. Tentative steps have been taken towards the construction of the tellurotocopherol structure by microwave-assisted radical cyclisation methodologies.

A combination of EPR and kinetic studies has been used to assess the antioxidant characteristics of selenotocopherol. A two-phase lipid peroxidation model revealed that the selenotocopherol is not catalytically regenerable. The same model has been used to assess the cooperativity of mixtures of tellurides with α-tocopherol and an aqueous thiol. It was seen that combinations of α-tocopherol with tellurides incorporating phenols displayed synergistic properties, and the mechanistic implications of this are discussed.

DSC measurements have been used to assess the antioxidant activity of tellurides together with coantioxidants in melts of polypropylene. The tellurides display excellent activity together with thiol or a sterically hindered phenol antioxidant. In chemiluminescence studies performed at lower temperatures, the telluride mixtures still outperform commercial blends, but to a lesser extent. In a synthetic oil a telluride has demonstrated promising antioxidant properties together with a thiol or phenolic antioxidant. However, under more realistic test conditions the telluride acts instead as a prooxidant. Some tellurides have been evaluated as antioxidants in paper. Water-soluble tellurides appear to function better than lipophilic tellurides, but neither is comparable in activity to α-tocopherol.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 75 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 123
Keyword
Organic chemistry, antioxidant, tellurium, selenium, computational design, homolytic substitution, radical cyclisation, microwave-assisted synthesis, antioxidant regeneration, Organisk kemi
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-6164 (URN)91-554-6410-6 (ISBN)
Public defence
2005-12-16, Room B42, BMC, Husargatan 3, Uppsala, 09:15
Opponent
Supervisors
Available from: 2005-11-25 Created: 2005-11-25 Last updated: 2013-07-31Bibliographically approved

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Ottosson, HenrikEngman, Lars

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