Synthesis of Regioselectively Protected Forms of Cytidine Based on Enzyme-catalyzed Deacetylation as the Key Step

N 4 -Acetylcytidine (77%) and 2′,3′-O,N 4 -triacetylcytidine (95%) were obtained from the hydrolysis of a common precursor, the peracetylated form of cytidine with Aspergillus niger lipase (Amano A) and Burkholderia cepacia esterase (SC esterase S), respectively, under very mild conditions. The experimental procedure for the conversion of triacetylcytidine to a corresponding phosphoramidite (82%), an intermediate for sugar nucleotide synthesis, is also elaborated.