Formycin Analogs II. Antiviral and Cytotoxic s-Triazolo [4, 3-a] - and [1, 5-a] Pyridine Derivatives

The novel N-bridgehead formycin analog 3- β-D-ribofuranosyl-8-amino-s-triazolo [4, 3-a] pyridine (8a-aza-4, 6-dideaza formycin) has been prepared from 5- [2, 3, 5-tri-O-benzoyl- β-D-ribofuranosyl] - (2H)-tetrazole and 2-chloro-3-nitropyridine. The synthetic route used an initial condensation followed by deprotection and subsequent hydrogenation to afford 2a. 2-Hydroxyethoxymethyl group, an acyclic group, that mimics the ribofuranose unit was also introduced. These compounds were tested against type 1 herpes and poliovirus in tissue culture and their effect on cellular RNA and DNA synthesis was determined. All derivatives possess considerable cytotoxic effect which is expressed more with ribofuranosyl derivatives.