a methyl group at the N-3 position of the functional group. Among them, the three thiourea derivatives (24, 26, and 38) and the six 2-cyanoguanidine derivatives (61, 62, 65, 75, 85, and 86) had the most potent antisecretory and/or antiulcer activities. These compounds are not histamineH2-receptorantagonists.