A Fourier transform infrared study of the electrophilic attack at the N7-site of guanosine-5′-monophosphate

Fourier transform infrared spectra of several N 7 -bound cations of guanosine-5′monophosphate disodium salt (5′-GMPNa 2 ), such as N 7 -H + GMP, N 7 -MeGMP, and N 7 -MGMP, where Me = CH 3 + and M = divalent metal ions, Cd, Mn, Co, Ni, Cu, Pt, and Mg, have been recorded and a correlation between the spectral changes and the nature of the electrophile (H + , CH 3 + , and M 2+ ) bound has been established. Spectroscopic evidence shows that methylation of the N 7 -position of 5′-GMPNa 2 causes larger perturbation on the guanine ring system than protonation or metalation, in the order Me + > H + > M 2+ . The effect of an N 7 -electrophilic attack on the vibrational frequencies of the purine, the sugar, and the phosphate group is discussed.