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

• Published in: Journal of medicinal chemistry 2010-11, Vol.53 (21), p.7804-7824
• Main Authors: Ji, Haitao, Delker, Silvia L, Li, Huiying, Martásek, Pavel, Roman, Linda J, Poulos, Thomas L, Silverman, Richard B
• Format: Article
• Language: English
• Subjects: Aminopyridines - chemical synthesis; Aminopyridines - chemistry; Animals; Catalytic Domain; Cattle; Crystallography, X-Ray; Drug Design; Isoenzymes - antagonists & inhibitors; Isoenzymes - chemistry; Models, Molecular; Nitric Oxide Synthase Type I - antagonists & inhibitors; Nitric Oxide Synthase Type I - chemistry; Protein Binding; Protein Conformation; Pyrrolidines - chemical synthesis; Pyrrolidines - chemistry; Rats; Stereoisomerism; Structure-Activity Relationship
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm100947x

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 of 8−34 and different binding conformations of the cis and trans isomers of 3 and 4, critical structural requirements of the NOS active site for ligand binding are revealed.