1-(4-(3-Chlorophenyl)thiazol-2-yl)guanidine Hydrobromide is used in the preparation of antiulcer agents, specifically 4-Substituted 2-guanidinothiazoles, which are reversible, competitive, and selective inhibitors of gastric H+,K+-ATPase. Also used in the preparation of substituted (thiazolylamino)tetrahydropyridopyrimidine derivatives useful as platelet aggregation inhibitors.