resulting C-5 lithiated species with various types of electrophiles furnish 5-substituted 6-phenylthiouridine derivatives. The phenylthio group in these products can be removed by a new type of desulfurizative stannylation with tributyltin hydride followed by protonolysis. The whole sequence constitutes a newroute to 5-substituted uridines. Application of this method to 2'-deoxyuridine is also described