Substituted 2-iminopiperidines as inhibitors of human nitric oxide synthase isoforms

A series of analogues of 2-iminopiperidine have been prepared and shown to be potent inhibitors of the human nitric oxide synthase (NOS) isoforms. Methyl substitutions on the 4-position (3) or 4- and 6-positions (8) afforded the most potent analogues. These compounds exhibited IC50 values of 0.1 and 0.08 microM, respectively, for hiNOS inhibition. Substitution with cyclohexylmethyl at the 6-position (13) afforded an inhibitor that showed the best selectivity for hiNOS versus heNOS (heNOS IC50/hiNOS IC50 = 64). Following oral administration, inhibitors were found to decrease serum nitrite/nitrate levels in an in vivo rat endotoxin assay. This series of 2-iminopiperidines were prepared via the described synthetic methodologies. The effect of ring substitutions on potency and selectivity for this class of cyclic amidines as NOS inhibitors is described.