Oxidation of pyrimidine nucleosides and nucleotides by osmium tetroxide

摘要: Abstract 1. Pyrimidine nucleosides such as thymidine, uridine or cytidine are oxidized readily at 0° by osmium tetroxide in ammonium chloride buffer. There is virtually no oxidation bicarbonate buffer of similar pH. Oxidation 1-methyluracil yields 5,6-dihydro-4,5,6-trihydroxy-1-methyl-2-pyrimidone. 2. Osmium and ammonia react reversibly aqueous solution to form a yellow 1:1 complex, probably OsO3NH. A second molecule must be involved the UMP since rate this reaction approximately proportional square concentration unprotonated ammonia. 3. 4-Thiouridine reacts with much more rapidly than does uridine. The changes absorption spectra different sodium They occur faster latter and, under suitable conditions, major product. 4. Polyuridylic acid ammoniacal tetroxide, but its inhibited polyadenylic acid. Pyrimidines yeast amino acid-transfer RNA slowly corresponding mononucleosides, especially thymine residues. Appreciable can without change sedimentation coefficient.