3-Oxo-s-triazolo[4,3-a]pyridine and various C-methyl derivatives (general structure 1) have been converted into the 2-β-D-ribofuranosyl species 2 and thence 4 via Friedel–Crafts catalyzed reaction with tetra-O-acetyl-β-D-ribofuranose, followed by deblocking. During the course of these reactions, rearrangements into the isomeric 3-β-D-ribofuranosyl-2-oxo-s-triazolo[1,5-a]-pyridines occur through ring-opening of the pyridine rings yielding species 3 and 5. The proportion of rearrangement products is dependent upon the position and number of the C-methyl substituents.Structural assignments for these compounds are based upon comparisons of spectroscopic properties (1H nmr, 13C nmr, uv) with model compounds from each isomeric series; structural assignments for these models are based on unequivocal mass-spectral fragmentation patterns. Unlike related triazolopyridine nucleosides with the ribose moiety attached to a pyridine nitrogen (Lynch and Sharma (1976)), there are no unusual aspects in the conformations of the nueleosides of types 4 and 5.
On the Mass Spectral Fragmentation of 2,5-Diphenyl-p-benzoquinones.
