The syntheses of l-/3-D-ribofuranosyl-4-oxopyrido [2,3-d] pyrimidine and 1-and 8-/3-n-ribofuranosy 1-2,4-dioxopyrido [2,3-d] pyrimidine are described. The site of ribosylation in each case is assigned by uv and pmr comparisons with requisite iV-methyl model compounds. The assignment of anomeric configuration is based upon pmr spectroscopy. A facile N-8 -> N-l ribosyl rearrangement is described.Significant antitumor activity against Walker muscular carcinosarcoma in rats has recently been demonstrated for 4-oxopyrido [2,3-d]pyrimidine2 (1, NSC 112518) and 2,4-dioxopyrido [2,3-d]pyrimidine2 (2, NSC 112519) . It was, therefore, of interest to undertake the synthesis of certain ribonucleoside derivatives of 1 and 2 as potential antitumor and antiviral agents.
The synthesis of three tricyclic nucleosides, 5R(7R)-9-oxo-3-/3-D-ribofuranosyl-l,2,4-triazolo[2,3-o]purine (3), 6,7-dimethyl-10-oxo-3-j3-D-ribofuranosyl-l,2,4-triazino[2,3-a]purine (4), and 10-oxo-3-5-D-ribofuranosyl-l,2,4-triazino[2,3-a]purine (5), is reported. These are structural analogs of the "Y" base of tRNA. The use of the nuclear Overhauser effect in proton assignment of 3 is described, as well as the fluorescence of 3 and 4. Covalent hydration of 5 is discussed.
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