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, *MP 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 4.5” and a 6-fold molar excess of periodate and cyclohexylamine, \kMP is degraded to inorganic phosphate and a mixture of Sformyluracil and 5-carboxyuracil. The apparent pK, values of S-formyluracil, calculated from ultraviolet absorption spectra at various pH values, are 6.8 and > 11.2. The same constants of S-carboxyuracil are 4.3,9.15, and > 13.2. Analysis of the spectral data shows that in both of these S-substituted uracil derivatives anion formation involves loss of a proton from N-l rather than from N-3 of the uracil ring.