Synthesis of 5- N - tert -butylaminoxylcytidine and EPR studies on its base pairing properties

5-N-tert-Butylaminoxylcytidine was synthesized as a new spin-labelled cytidine to detect guanosine by EPR spectroscopy. Metal-halogen exchange reaction of TBS-protected N-benzoyl-5-iodocytidine followed by a reaction with 2-methyl-2-nitrosopropane afforded 5-N-tert-butylhydroxylaminocytidine with considerable affinity for guanosine and its oxidation gave 5-N-tert-butylaminoxylcytidine. Changes in EPR parameters monitored its selective base pairing with guanosine derivatives and the formation of a 2:2 complex with 8-oxoguanosine.