4-Amino-1-(2, 3-dideoxy-β-D-glycero-pentofuranosyl)-1H-pyrazolo [3, 4-d] pyrimidine (5) was synthesized from 8-aza-7-deaza-2'-deoxyadenosine (1). Benzoylation of the 4-amino group of 1 followed by 4, 4'-dimethoxytritylation of the 5'-hydroxyl function gave 2b. Barton