CALCULATION OF TAUTOMER PREFERENCE FOR RIGID IMIDAZOLE DERIVATIVES

The tautomeric preference of rigid imidazole derivatives has been anal yzed theoretically from molecular orbital calculations ab initio. The present results indicate that the reduced potencies exhibited by imida zolylphenylene analogues of cimetidine and metiamide at the H2-recepto r are consistent with those hypotheses that defined the N3-H tautomer of the monocation as the only recognizable species in this class of hi stamine H2-ligand. However, our results suggest that the 4-methylimida zolylphenylene analogue of cimetidine could be an effective histamine H3-antagonist.