S,X-acetals in nucleoside chemistry.  III.  Synthesis of 2'- and 3'-O-azidomethyl derivatives of ribonucleosides. 
2'- and 3'-O-azidomethyl derivatives of ribonucleosides were obtained by splitting the corresponding methylthiomethyl derivatives of ribonucleosides with bromine or SO2Cl2 followed by lithium azide treatment.