Mercuration effects on nucleoside chemical shifts: 15 N and 13 C NMR studies of methylmercury(II) ion addition to cytidine‐3′‐monophosphate and guanosine‐5′‐monophosphate

Methylmercuration of cytidine‐3′‐monophosphate is shown to occur at the N‐3 site, resulting in a substantial upfield shift in the 15 N resonance of this nitrogen. For guanosine‐5′‐monophosphate the 15 N NMR data show N‐1 to be the site of complexation of CH 3 Hg + at pH 8. The large downfield shift observed for N‐1 as a result of this binding is explained in terms of a concomitant deprotonation phenomenon. Changes in 13 C NMR chemical shifts on methylmercuration are less pronounced, but consistent with these binding sites.