The reaction of uridine, N 4-benzoylcytidine, guanosine, and N 6-p-toluoyladenosine with diethyl azodicarboxylate and triphenylphosphine resulted in the formation of the corresponding 2′, 3′-O-(triphenylphosphoranediyl)-cyclonucleosides. On the other hand, adenosine afforded, under similar conditions, 3′, 5′-O-(triphenylphosphoranediyl) adenosine (19). The difference can be explained in terms of the acidity of base moieties of ...