Abstract Regioselective glycosylation of 4-methoxy-1H-pyrazolo [3, 4-d] pyrimidine (6b) with the halogenose 7 was achieved by employing phase-transfer techniques. The N-1 glycosylation product 3a was formed in preponderance. It was converted into the allopurinol β-D-2′-deoxyribonucleoside 2.