Organoselenium compounds find applications in organic synthesis, materials synthesis, ligand chemistry and biologically relevant processes. This review deals with the use of various synthetic organoselenium compounds as mimics of glutathione peroxidase (GPx), a selenoenzyme which catalyses the reduction of a variety of hydroperoxides and protects the cell membranes from oxidative damage. The mechanism by which these compounds catalyse the reduction of peroxides is also reviewed. The cyclic selenenamides and diselenides with suitably positioned substituents exert their catalytic activity by a mechanism similar to that of the natural enzyme.

intramolecular interactions. She received her Ph.D. degree from the University of Bristol (2004), under the supervision of Professor R. P. Evershed, where she continued to work on a Wellcome Trust Research Fellowship in Bioarchaeology until July 2007. Since then Anna has worked in the water industry as a drinking water quality scientist.

The synthesis, structure, and thiol peroxidase-like antioxidant activities of several diaryl diselenides having intramolecularly coordinating amino groups are described. The diselenides derived from enantiomerically pure R-(+)- and S-(−)-N,N-dimethyl(1-ferrocenylethyl)amine show excellent peroxidase activity. To investigate the mechanistic role of various organoselenium intermediates, a detailed in situ characterization of the intermediates has been carried out by 77Se NMR spectroscopy. While most of the diselenides exert their peroxidase activity via selenol, selenenic acid, and selenenyl sulfide intermediates, the differences in the relative activities of the diselenides are due to the varying degree of intramolecular Se···N interaction. The diselenides having strong Se···N interactions are found to be inactive due to the ability of their selenenyl sulfide derivatives to enhance the reverse GPx cycle (RSeSR + H2O2 = RSeOH). In these cases, the nucleophilic attack of thiol takes place preferentially at selenium rather than sulfur and this reduces the formation of selenol by terminating the forward reaction. On the other hand, the diselenides having weak Se···N interactions are found to be more active due to the fast reaction of the selenenyl sulfide derivatives with thiol to produce diphenyl disulfide and the expected selenol (RSeSR + PhSH = PhSSPh + RSeH). The unsubstituted diaryl diselenides are found to be less active due to the slow reactions of these diselenides with thiol and hydrogen peroxide and also due to the instability of the intermediates. The catalytic cycles of 18 and 19 strongly resemble the mechanism by which the natural enzyme, glutathione peroxidase, catalyzes the reduction of hydroperoxides.