Electrochemical reduction of uridine in dimethyl sulfoxide: effect of the ribose group

Abstract

The easier electrochemical reduction of uridine (1-[beta]-D-ribofuranosyluracil) in dimethyl sulfoxide as compared to uracil (2, 4-dihydroxypyrimidine) by ca. 0.1 V is explicable on the basis of the electron-withdrawing effect of the ribose group. This effect and possible steric hindrance by the ribose group markedly affect the reaction sequence following the initial one-electron reduction to generate a radical anion, which abstracts a proton from the parent uridine (father--son reaction) to form the neutral uridine free radical and the uridine anion. With increasing uridine concentration, further reduction and protonation reactions are favored, resulting in an increase in the effective faradaic n from ca. 0.5 to 0.8. The availability of only one proton-donating site on uridine, ie, that on N(3), allows explication of the behavior of other hydroxypyrimidines such as uracil.