Preparation and use as spin trapping agents of new ester-nitrones

The synthesis of two new nitrones, N-benzylidene-1,1-bis(ethoxycarbonyl)ethylamine N-oxide (DEEPN) and N-[(1-oxidopyridin-1-ium-4-yl)methylidene]-1-ethoxycarbonyl-1- methylethylamine N-oxide (EPPyON), is described. Measurement of their n-octanol-phosphate buffer partition coefficient permitted evaluation of their lipophilicity. Their capacity to act as spin trapping agents was investigated in aqueous media. Although these nitrones were unsuitable for detecting hydroxyl radical, they efficiently trapped various carbon- and oxygen-centred radicals, including superoxide, in aqueous media. The half-lives of their superoxide adducts were determined at pH 5.8 and 7.2. At neutral pH, the superoxide spin adduct of DEEPN was found to be as persistent as that of 5-diethoxyphosphoryl-5-methyl-3,4-dihydropyrrole N-oxide (DEPMPO). Consequently, DEEPN was believed to be an efficient trap for superoxide detection in aqueous media.