Synthesis of a Protected keto-Lysidine Analogue via Improved Preparation of Arabino-isoCytosine Nucleosides.

Anhydrouridines react with aliphatic amines to give N-alkyl isocytosines, but reported procedures often demand very long reaction times and can be low yielding, with narrow scope. A modified procedure for such reactions has been developed, using microwave irradiation, significantly reducing reaction time and allowing facile access to a diverse range of novel nucleosides on the gram scale. The method has been used to prepare a precursor to a novel analogue of lysidine, a naturally occurring iminonucleoside found in tRNA.