Abstract
1. Osmium tetroxide in dilute ammonia oxidizes various pyrimidine nucleosides at different rates. Thymidine is oxidized about 45 times as fast as deoxycytidine. The phosphate groups may be eliminated from oxidized thymine nucleotides by successive treatments with alkali and then with diphenylamine in aqueous formic acid. The reactions can be applied to the selective degradation of thymidine in oligodeoxynucleotides.