Acyclic analogues of purine nucleosides: One- and two-dimensional H-1 and C-13 NMR evidences for N-9 and N-7 regioisomers

It has been established by means of one- and two-dimensional H-1 and C-13 NMR spectroscopy that adenine acyclonucleosides are substituted at either N-9 or N-7 with 2',3'-dihydroxyprop-1-yl (2 and 3) or 2'-hydroxyprop-1-yl (4 and 5) aliphatic chains. The N-3 isomer has not been formed, as claimed previously. This was deduced on the basis of chemical shifts, substituent induced chemical shifts, magnitude and multiplicity of C-H couplings as well as connectivities in 2D homo- and heteronuclear correlation spectra.