Amino acid amides of 2-[(2-aminobenzyl)sulfinyl]benzimidazole as acid-stable prodrugs of potential inhibitors of H+K+ ATPase

A series of amino acid amides of 2-[(2-aminobenzyl)sulfinyl]benzimidazole were prepared and found to possess gastric antisecretory activity on oral administration. (Glycylaminobenzyl)sulfinyl compound 23a, stable in artificial gastric juice (pH 1.2), was given orally to dogs. It was absorbed efficiently and converted into aniline derivative 7a which showed a very high plasma concentration. Compound 23a was hydrolyzed by the action of aminopeptidase present in plasma or the brush border fraction of the small intestine to release the terminal glycine. o-Aniline derivatives showed good activity in in vitro, H + K + -ATPase inhibition as well as in the inhibition of histamine stimulated acid secretion in isolated bullfrog gastric mucosa. Although these o-aniline derivatives showed no or weak gastric antisecretory activity in rat by id administration, they were active when administered ip. Therefore, these amino acid amides were considered to be acid stable prodrugs of proton pump inhibiting o-aniline derivatives. The mechanism of H + K + -ATPase inhibition of 7a was also examined.