Syntheses of specifically 15N-labeled adenosine and guanosine

This unit describes the specific incorporation of (15)N into the N7 and amino positions of adenosine, and conversion of the adenosine to guanosine labeled at the N1, N7, and amino positions. Two variations of the procedures are also presented that include either (12)C or (13)C at the C8 position of adenosine, and (13)C at either the C8 or C2 position of guanosine. These (13)C tags permit the incorporation of two (15)N-labeled nucleosides into an RNA strand while ensuring that their nuclear magnetic resonance (NMR) signals can be distinguished from each other by the presence or absence of C-N coupling. While the major application of these specifically (15)N-labeled nucleosides is NMR, the additional mass makes them useful in mass spectrometry (MS) as well. The procedures can also be adapted to synthesize the labeled deoxynucleosides. A support protocol describes the synthesis of 7-methylguanosine.