Exploration of the Active Site of Neuronal Nitric Oxide Synthase by the Design and Synthesis of Pyrrolidinomethyl 2-Aminopyridine Derivatives.

Neuronal nitric oxide synthase (nNOS) represents an important therapeutic target for the prevention of brain injury and the treatment of various neurodegenerative disorders. A series of trans-substituted amino pyrrolidinomethyl 2-aminopyridine derivatives (8−34) was designed and synthesized. A structure−activity relationship analysis led to the discovery of low nanomolar nNOS inhibitors ((±)-32 and (±)-34) with more than 1000-fold selectivity for nNOS over eNOS. Four enantiomerically pure isomers of 3′-[2′′-(3′′′-fluorophenethylamino)ethoxy]pyrrolidin-4′-yl}methyl}-4-methylpyridin-2-amine (4) also were synthesized. It was found that (3′R,4′R)-4 can induce enzyme elasticity to generate a new “hot spot” for ligand binding. The inhibitor adopts a unique binding mode, the same as that observed for (3′R,4′R)-3′-[2′′-(3′′′-fluorophenethylamino)ethylamino]pyrrolidin-4′-yl}methyl}-4-methylpyridin-2-amine ((3′R,4′R)-3) (J. Am. Chem. Soc. 2010, 132 (15), 5437−5442). On the basis of structure−activity relationships ...