title: Synthesis and antioxidant profile of all-rac-alpha-selenotocopherol.
abstract: all-rac-alpha-Selenotocopherol (6c) has been synthesized in 11 steps in 6.6% total yield. Key steps include chloromethylation to approach the persubstituted aromatic 9b and cyclization of alcohol precursor 10 by radical homolytic substitution at selenium to form the selenotocopherol heterocycle. Determination of the OH bond dissociation enthalpy (BDE) of 6c by electron paramagnetic resonance (EPR) equilibration techniques gave a value of 78.1 +/- 0.3 kcal mol(-1), approximately 1 kcal mol(-1) higher than that of alpha-tocopherol. Kinetic studies performed by measuring oxygen uptake of the induced oxidation of styrene in the presence of an antioxidant showed that selenotocopherol (6c) was a slightly poorer inhibitor than alpha-tocopherol, in agreement with the BDE values. In contrast to simpler selenotocopherol analogues, 6c was not regenerable in the presence of a stoichiometric coreductant in a two-phase lipid peroxidation model.
authors.affiliation: Department of Chemistry, Organic Chemistry, Box 599, Uppsala University, SE-751 24 Uppsala, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Shanks
authors.forename: Riccardo
authors.initials: R
authors.lastname: Amorati
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Fumo
authors.forename: Gian Franco
authors.initials: GF
authors.lastname: Pedulli
authors.forename: Luca
authors.initials: L
authors.lastname: Valgimigli
authors.forename: Lars
authors.initials: L
authors.lastname: Engman
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D018036:Selenium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D024505:Tocopherols / Q000138:chemical synthesis* / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D018036:Selenium Compounds; C512020:all-rac-alpha-selenotocopherol; D014867:Water; D024505:Tocopherols; D010100:Oxygen