Studies on antiulcer agents. III. Plausible mechanism of antisecretory action of ethyl 2-[(1h-benzimidazol-2-yl)sulfinylmethyl]-4-dimethylamino-5- pyrimidinecarboxylate, an H+/K+-ATPase inhibitor, based on its reaction with thiols

Article abstract of DOI:10.1248/cpb.43.1985

To explore the mechanism of the gastric antisecretion activity of ethyl 2- [(1H-benzimidazol-2-yl)sulfinylmethyl]-4-dimethylamino-5- pyrimidinecarboxylate (5), a potential H⁺/K⁺-ATPase inhibitor, in the acid compartment of parietal cells, its reaction with some alkylthiols in the presence of hydrochloric acid was investigated. Upon treatment with 2- mercaptoethanol under acidic conditions, 5 gave a characteristic 1:2 adduct, ethyl 4-[2-(2-hydroxyethyldithio)-1-(2- hydroxyethylthio)ethylidenamino]pyrimido[1,2-a]benzimidazole-3-carboxylate (6), instead of providing a disulfide of type 3, 2-(2- alkyldithiomethylpyridino)benzimidazolide, the product predicted to be formed according to the reaction mechanism of common H⁺/K⁺-ATPase inhibitors, such as omeprazole or lansoprazole, with mercaptans. With a large excess of 2- mercaptoethanol, 5 provided 2-(2-hydroxyethylthio)-1H-benzimidazole (8) and ethyl 4-dimethylamino-2-(2-hydroxyethyldithio)-5-pyrimidinecarboxylate (9) as well as 6. The transformation mechanisms and their implications are discussed.

Full text of DOI:10.1248/cpb.43.1985

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