Synthesis of intramolecularly coordinated cyclic selenenate/thioselenenate esters and their glutathione peroxidase-like activity

The syntheses and characterization of selenenate esters, thioselenenate ester and related derivatives are described. The reactions of n-butyl-4-tert-2,6-di(formyl)phenyl selenide (23) or bis(2,6-diformyl-4-tert-butylphenyl)diselenide (24) with bromine affords a new selenenate ester, 5-tert-butyl-7-(formyl)benzoxaselenol-3-one (25), stabilized by ortho-formyl group along with 3,3′-oxybis(5-tert-butyl-3H-benzo[c][1,2]oxoselenole-7-carbaldehyde) (16). Oxidation of (25) with H2O2 gives 5-tert-butyl-7-(carboxylic)benzoxaselenol-3-one-Se-oxide (26). However, the direct oxidation of (23) with H2O2 affords 5-tert-butyl-7-(butylcarboxylate)benzoxaselenol-3-one (27). The synthesis of 5-tert-butyl-7-(methylcarboxylate) benzothiaselenol-3-one (28) has been accomplished by the reaction of (26) with thionyl chloride (SOCl2) with a catalytic amount of N, N-dimethylformamide. Attempted thionation of 7-nitro-1,2-benzisoselenole(3H)-Se-oxide (20) leads to the isolation of bis(2-chloromethyl-6-nitrophenyl)diselenide (29). The presence of intramolecular secondary Se···O interactions in all the esters is confirmed by single crystal X-ray diffraction studies and computational studies. Glutathione peroxidase-like activity of (16), (25)-(29) has been determined by the coupled reductase assay.