Periodate Oxidation of Pseudouridine 5'-Phosphate and Spectral Characterization of the Products

Under the conditions for oxidative degradation, with a 2-fold molar excess of periodate and cyclohexylamine at room temperature, ψMP is degraded to inorganic phosphate but fails to release the base. In this latter respect, the parent pseudouridine behaves similarly. Under more drastic conditions, with a prolonged treatment at 45° and a 6-fold molar excess of periodate and cyclohexylamine, ψMP is degraded to inorganic phosphate and a mixture of 5-formyluracil and 5-carboxyuracil. The apparent pK a values of 5-formyluracil, calculated from ultraviolet absorption spectra at various pH values, are 6.8 and >11.2. The same constants of 5-carboxyuracil are 4.3,9.15, and >13.2. Analysis of the spectral data shows that in both of these 5-substituted uracil derivatives anion formation involves loss of a proton from N-1 rather than from N-3 of the uracil ring.