A method for producing a .beta.-enriched protected decitabine comprising: a) coupling a protected 2-deoxy-ribofuranose with a protected 5-azacytosine in the presence of a catalyst to form a reaction mixture comprising the protected decitabine of formula I; and b) quenching the reaction mixture of step a) with a base. The .beta.-enriched protected decitabine so made may be deprotected to produce a decitabine product in a high yield and purity.