Synthesis and biological activity of certain 1,2,3-triazole carboxamide nucleosides related to bredinin and pyrazofurin.

5-Hydroxy-1-(beta-D-ribofuranosyl)-1,2,3-triazole-4-carboxamide (II) has been prepared by direct glycosylation of the trimethylsilyl derivative of 5-hydroxy-1,2,3-triazole-4-carboxamide (IV). The use of trimethylsilyltrifluoromethane sulfonate as a catalyst and 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose in acetonitrile gave a 95% yield of a 1:1 mixture of V and VI as blocked nucleosides which were readily separated on a silica gel column. The synthesis of II was also achieved by the cycloaddition of 2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl azide with ethyl malonamate. II shows significant antiviral activity against herpes and measles virus in vitro.

Synthesis and antiviral acticity of some phosphates of the broad-spectrum antiviral nucleoside, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (ribavirin).

1-beta-D-Ribofuranosyl-1,2,4-triazole-3-carboxamide 5'-phosphate (2) was prepared and converted into the following derivatives: the 5'-phosphoramidate 3, the 5'-diphosphate 4, the 5'-triphosphate 5, and the cyclic 3',5'-phosphate 6. The cyclic 2',3'-phosphate 7 was prepared from the parent nucleoside, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (1), and was opened to the 2'(3')-phosphate 8. These compounds were found to exhibit significant antiviral activity against several viruses in cell culture. Ribavirin 5'-phosphate (2) was shown to be effective when tested against lethal infections in mice caused by influenza A2, influenza B, and murine hepatitis viruses.

Synthesis and biochemical evaluation of nucleosides of naphthoquinone heterocycles.

The synthesis, characterization, and biochemical evaluation of 1-beta-D-ribofuranosylnaphtho[2,3-d]imidazole-4,9-dione (3), 2-beta-D-ribofuranosylnaphtho[2,3-d]pyrazole-4,9-dione (6), and 2-beta-D-ribofuranosylnaphthol[2,3-d]triazole-4,9-dione (9) are reported. These quinone nucleosides and the corresponding quinone heterocycles were tested as inhibitors of purine nucleotide biosynthesis in Ehrlich ascites cells. The nucleosides 3 and 9 and naphtho[2,3-d]imidazole-4,9-dione were effective inhibitors of hypoxanthine phosphoribosyltransferase.

Synthesis and antiviral activity of certain thiazole C-nucleosides.

A general reaction of glycosyl cyanides with liquid hydrogen sulfide in the presence of 4-dimethylaminopyridine to provide the corresponding glycosylthiocarboxamides is described. These glycosylthiocarboxamides were utilized as the precursors for the synthesis of 2-D-ribofuranosylthiazole-4-carboxamide and 2-beta-D-ribofuranosylthiazole-5-carboxamide (23). The structural modification of 2-beta-D-ribofuranosylthiazole-4-carboxamide (12) into 2-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)thiazole-4-carboxamide (15), 2-beta-D-ribofuranosylthiazole-4-thiocarboxamide (17), and 2-(5-deoxy-beta-D-ribofuranosyl)thiazole-4-carboxamide (19) is also described. These thiazole nucleosides were tested for in vitro activity against type 1 herpes virus, type 3 parainfluenza virus, and type 13 rhinovirus and an in vivo experiment was run against parainfluenza virus. They were also evaluated as potential inhibitors of purine nucleotide biosynthesis. It was shown that the compounds (12 and 15) which possessed the most significant antiviral activity were also active inhibitors (40-70%) of guanine nucleotide biosynthesis.

Effect of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (ribavirin) on Friend leukemia virus infections in mice.

Ribavirin, when administered intraperitoneally to mice infected with Friend leukemia virus, significantly inhibited development of the disease as determined by inhibition of virus-induced splenomegaly and viable virus titers in the spleen and plasma of the infected animals. The drug was effective whether administered ip in multiple daily treatments, treatments every three days, or single injection. Greatest efficacy was seen when therapy began early in the infection, presumably while the virus was in its eclipse phase.

Mechanism of action of 1- -D-ribofuranosyl-1,2,4-triazole-3-carboxamide (Virazole), a new broad-spectrum antiviral agent.

The antiviral activity of the synthetic nucleoside, Virazole (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), against measles virus in Vero cell cultures was substantially reversed by xanthosine, guanosine, and to a slightly lesser extent by inosine. Virazole 5'-phosphate was subsequently found to be a potent competitive inhibitor of inosine 5'-phosphate dehydrogenase (IMP:NAD(+) oxidoreductase, EC 1.2.1.14) isolated from Escherichia coli (K(m) = 1.8 x 10(-5) M) with a K(i) of 2.7 x 10(-7) M. Guanosine 5'-phosphate (GMP) was a competitive inhibitor of this enzyme with a K(i) of 7.7 x 10(-5) M. Virazole 5'-phosphate was similarly active against IMP dehydrogenase isolated from Ehrlich ascites tumor cells, with a K(i) of 2.5 x 10(-7) M. The K(m) for this enzyme was 1.8 x 10(-5) M, and the K(i) for GMP was 2.2 x 10(-4) M. These results suggest that the antiviral activity of Virazole might be due to the inhibition of GMP biosynthesis in the infected cell at the step involving the conversion of IMP to xanthosine 5'-phosphate. This inhibition would consequently result in inhibition of the synthesis of vital viral nucleic acid.

In vitro effect of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (virazole, ICN 1229) on deoxyribonucleic acid and ribonucleic acid viruses.

Virazole (1-beta-d-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a highly soluble new synthetic nucleoside having significant, reproducible activity against a broad spectrum of deoxyribonucleic acid and ribonucleic acid viruses in vitro. The drug inhibited viral cytopathogenic effects in monolayers of cells infected for 3 days with type 3 adeno, types 1 and 2 herpes, myxoma, cytomegalo, vaccinia, infectious bovine rhinotracheitis, types 1A, 2, 8, 13, and 56 rhino, types 1 and 3 parainfluenza, vesicular stomatitis, subacute sclerosing panencephalitis, Semliki Forest, Newcastle disease, and measles viruses. Hemagglutinin production by influenza A(2), influenza B, and type 1 parainfluenza viruses in chicken embryo cells was reduced by Virazole treatment. Recoverable intra- and extracellular virus titers were reduced by the drug in experiments with type 1 herpes, vaccinia, type 3 parainfluenza, and vesicular stomatitis viruses. Plaque formation by type 1 herpesvirus was also inhibited by exposure of the infected cells to Virazole. Pretreatment of cells with the compound, followed by its removal before addition of type 1 herpesvirus, severely lessened the antiviral activity; the compound was still moderately effective in reducing the viral effects on the cells when added as long as 22 hr after the virus. Parallel experiments, in which the antiviral activity of a number of known active drugs was compared, indicated Virazole to have at least a comparable degree of activity, and it was also active against a wider variety of viruses than any of these known active materials. The CCED(50) of Virazole to chicken embryo cells was approximately 1,000 mug/ml, although concentrations as low as 10 mug/ml caused slight (15%) inhibition in total cellular protein after 72 hr of incubation.

Broad-spectrum antiviral activity of Virazole: 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide.

Virazole is a synthetic nucleoside active in tissue culture against at least 16 DNA and RNA viruses. Applied topically, it inhibits herpetic keratitis in rabbits and tail lesions induced by herpes, vaccinia, and vesicular stomatitis viruses in mice. Injected intraperitoneally into mice, it inhibits splenomegaly and hepatomegaly induced by Friend leukemia virus and respiratory infections caused by influenza A(O), A(2), and B viruses and parainfluenza 1 virus. infections is also effective.