The syntheses and properties of 8-aza-7-deazapurine (pyrazolo [3, 4-d] pyrimidine) ribonucleosides related to 2-aminoadenosine and isoguanosine are described. Glycosylation of 8-aza-7-deazapurine-2, 6-diamine 5 with 1-O-acetyl-2, 3, 5-tri-O-benzoyl-β-