Ozonolysis of thymidine: isolation and identification of the main oxidation products

The ozone-mediated oxidation of thymidine was investigated on the basis of final product identification. The oxidation reaction gave rise to five major modified nucleosides which were isolated and characterised from extensive 1H NMR and mass spectrometry studies. The comparison with the current knowledge of the hydroxyl radical-mediated oxidation reactions of thymidine in aerated aqueous solution indicates that the formation of ozone oxidation products may be mostly explained in terms of initial generation of an ozonide. Indeed, the identified products obtained by ozonolysis of thymidine resulted from the opening of the pyrimidine C5-C6 bond.