5′-Protected 3′-amino-2′, 3′-dideoxynucleosides containing any of the four canonical nucleobases (A/C/G/T) were prepared via azides in five to six steps, starting from deoxynucleosides. For pyrimidines, the synthetic route involved nucleophilic opening of anhydronucleosides. For purines, an in situ oxidation/reduction sequence, followed by a Mitsunobu reaction with diphenyl-2-pyridylphosphine and sodium azide, provided the 3′- ...