Nicotinamide Derivatives as a New Class of Gastric H<sup>+</sup>/K<sup>+</sup>-ATPase Inhibitors. 1. Synthesis and Structure−Activity Relationships of <i>N</i>-Substituted 2-(Benzhydryl- and benzylsulfinyl)nicotinamides
compounds are converted into their active forms, 2,3-dihydro-3-oxoisothiazolo[5,4-b]pyridines 5, which inhibitgastricH+/K(+)-ATPase. Inhibitory activities against [14C]aminopyrine accumulation stimulated by dibutyryl cAMP in isolated rabbit parietal cells in vitro and histamine-induced gastric acid secretion in pylorus-ligated rats by intraduodenal administration in vivo were evaluated, and the structure-activity