Synthesis of a New Spin Trap: 2-(Diethoxyphosphoryl)-2-phenyl-3,4-dihydro-2<i>H</i>-pyrrole 1-Oxide

Abstract

Recently, the synthesis of a new phosphorylated nitrone, 2-(diethoxyphosphoryl)-2-methyl-3,4-dihydro-2H-pyrrole 1-oxide (DEPMPO) (2) was described. The presence of the phosphorylated group strongly stabilized the DEPMPO-superoxide spin adduct. To understand the role of the diethoxyphosphoryl group in this stabilization, a new phosphorylated nitrone, 2-(diethoxyphosphoryl)-2-phenyl-3,4-dihydro-2H-pyrrole 1-oxide (DEPPPO) (7), was prepared through a four-step synthetic pathway, and its ability to trap free radicals was investigated. Data obtained from spin trapping experiments of a wide variety of free radicals generated in situ showed the formation of two diastereoisomers spin adducts with different phosphorus and hydrogen coupling constants. Superoxide trapping by DEPPPO gave a persistent nitroxide spin adduct, and its half-time life was measured and compared to that of the DEPMPO analogue.