Development of new amination reaction at 4-position of pyrimidine nucleosides

A new method for the syntheses of the 4-aminopyrimidine nucleosides (la, b) has been developed. The method consists of conversion of uridines into quaternary-ammonium intermediates (4a, b) by the reaction with p-toluenesulfonyl chloride(TsCl) in the presence of tertiary-amin es, followed by amination with aq NH3. The method is expedient for large-scale preparation of cytidines like 2'-deoxycytidine (la) or 2'-deoxy-5methylcytidine (lb).