Nucleosides. Part LVI. Aminolysis of carbamates of adenosine and cytidine

Abstract The 2‐(4‐nitrophenyl)ethoxycarbonyl(npeoc) group, introduced 1984 as protecting group for exocyclic amino functions of nucleic‐acid bases, reacts with amines under mild conditions to urea derivatives. Treatment of 2′,5′‐di‐ O ‐acetyl‐ N 6 ‐[2‐(4‐nitrophenyl) ethoxycarbonyl]cordycepin ( 3 ) with NH 3 /MeOH overnight at room temperature affords cordycepin ( 4 ) and N 6 ‐carbamoylcordycepin ( 5 ). Preliminary investigations towards the elucidation of the reaction mechanism indicate that the aminolysis proceeds via an addition‐elimination or an isocyanate mechanism, depending on the reaction conditions. The phenoxycarbonyl (phoc) group at N 6 or N 4 was chosen to study the mild conversion of carbamates with aromatic amines into ureas of adenosine and cytidine, respectively.