STEREOCHEMISTRY OF CHARGED NITROGEN AROMATIC INTERACTIONS AND ITS INVOLVEMENT IN LIGAND RECEPTOR-BINDING

Recently, new evidence was found for the involvement of charged nitrog en-aromatic interactions in ligand-receptor binding. In this study we report two favourable orientations of a phenyl ring with respect to a R-N+(CH3)3 group, based on crystal structure statistics from the Cambr idge Structural Database. In the first orientation, the phenyl ring is situated in between the substituents at about 4.5 angstrom from the n itrogen atom, and the ring is approximately oriented on the sphere aro und the nitrogen atom. In the second orientation, the phenyl ring is s ituated in the same direction as one of the N-C bonds at about 6.0 ang strom from the nitrogen atom, and the ring is tilted with respect to t he sphere around the nitrogen atom. The same two orientations were als o found in the crystal structures of three ligand-receptor complexes, which implies that these orientations probably play a major role in mo lecular recognition mechanisms.