A simple method for N-acylation of adenosine and cytidine nucleosides using carboxylic acids activated in-situ with carbonyldiimidazole

Carboxylic acids are activated with 1,1'-carbonyldiimidazole in acetonitrile to form N-acylimidazoles which are then treated with per-trimethylsilyl ethers of nucleosides adenosine or cytidine at ambient temperature to generate exclusively N-acylated-Adenosine or N-acylated-Cytidine derivatives.