The two step synthesis of 5'-O- and 3'-O-(N-alkylcarbamoyl)-nucleosides is described. The key step is the enzymatic synthesis of 5'-O- or 3'-O-alkoxycarbonylnucleoside in a regioselective way. In a second aminolysis step these carbonates yield the corresponding urethanes. This methodology allows to assemble aminoalcohols and L-amino acids to 2'-deoxynucleosides.