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

Article abstract of DOI:10.1002/hlca.19940770509

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-N⁶-[2-(4-nitrophenyl)ethoxycarbonyl]cordycepin (3) with NH₃/MeOH overnight at room temperature affords cordycepin (4) and N⁶-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 N⁶ or N⁴ was chosen to study the mild conversion of carbamates with aromatic amines into ureas of adenosine and cytidine, respectively.