Discovery of N‑(4-Aminobutyl)‑N′‑(2-methoxyethyl)guanidine as the First Selective, Nonamino Acid, Catalytic Site Inhibitor of Human Dimethylarginine Dimethylaminohydrolase‑1 (hDDAH-1)

N-(4-Aminobutyl)-N′-(2-methoxyethyl)­guanidine (8a) is a potent inhibitor targeting the hDDAH-1 active site (Ki = 18 μM) and derived from a series of guanidine- and amidine-based inhibitors. Its nonamino acid nature leads to high selectivities toward other enzymes of the nitric oxide-modulating system. Crystallographic data of 8a-bound hDDAH-1 illuminated a unique binding mode. Together with its developed N-hydroxyguanidine prodrug 11, 8a will serve as a most widely applicable, pharmacological tool to target DDAH-1-associated diseases.