New Acyclic Purine Nucleoside Analogues Containing Exocyclic Pyrrolo Moiety: Synthetic, NMR and X-ray Crystal Structure Studies

The synthesis of novel 6-(N-pyrrolyl)purine nucleoside analogues containing acyclic side chains attached to the purine ring at N-9 is described. The structures were determined by 1H and 13CNMR on the basis of chemical shifts, substituent induced shifts, C-H coupling constants and connectivity in the COSY,NOESY and HETCOR spectra. Unequivocal proof for the stereostructure of 6 was obtained by its X-ray crystallographic analysis. Geometrical data from X-ray structural analysis showed that the two 6-(N-pyrrolyl) purine rings involved in the skeleton of 6 are anti-disposed but not centrosymmetric with respect to the central aliphatic bridge.