Reaction of purine nucleosides, such as 2',3'-O-isopropylideneinosine 1a and 2',3'-O-isopropylideneadenosine 1c, with diisobutylaluminum hydride in dry tetrahydrofuran resulted in the reductive cleavage of the ribose moiety at the anomeric position to give the corresponding 9-(2',3'-O-isopropylideneribityl)purines 2a, c in good yields.