Studies on antiulcer drugs. IV. Synthesis and antiulcer activities of imidazo[1,2-a]pyridinylethylbenzothiazoles and -benzimidazoles.

A series of 6-[2-(imidazo[1,2-a]pyridin-2-yl)ethyl]benzothiazoles (II) and benzimidazole analogues (III) was synthesized and tested for histamine H2-receptor antagonist, gastric antisecretory and anti-stress ulcer activity. A benzimidazole derivative (IIIa) exhibited strong antisecretory activity, whereas the corresponding benzothiazole derivative (IIb) lacked this potency in in vivo test. In contrast to compound IIIa, however, compound IIb demonstrated good inhibition against stress induced ulcer. The structure-activity relationships of these compounds are discussed.