Abstract: An optically active pyrrolopyridazine compound of the formula (I) or a pharmaceutically acceptable salt thereof: wherein R1 is alkyl; R2 and R3 are each independently alkyl; R4 is optionally substituted aryl; and A is imino, oxygen or sulfur. The pyrrolopyridazine compound or pharmaceutically acceptable salts thereof of the present invention exhibit excellent gastric acid secretory inhibition activity and gastric mucous membrane protection activity, as well as excellent antibacterial activity against Helicobacter pylori. They are useful medicines and are particularly useful for treating or preventing ulcerative diseases.

Abstract: An optically active pyrrolopyridazine compound of the formula (I) or a pharmaceutically acceptable salt thereof: 1

Abstract: 5-Alkoxy-2(3H)-oxazolone compounds represented by general formula (1); and a R.sup.1 process for the preparation thereof, wherein R.sup.1 is hydrogen, optionally substituted C.sub.1 -C.sub.10 alkyl, optionally substituted C.sub.3 -C.sub.10 cycloalkyl, optionally substituted C.sub.2 -C.sub.10 alkenyl or optionally substituted phenyl; R.sup.2 is hydrogen, optionally substituted C.sub.1 -C.sub.10 alkyl, optionally substituted phenyl or unsubstituted C.sub.2 -C.sub.10 alkenyl; R.sup.3 is optionally substituted C.sub.1 -C.sub.10 alkyl, optionally substituted C.sub.3 -C.sub.10 cycloalkyl, optionally substituted C.sub.2 -C.sub.10 alkenyl excluding 2-alkenyl, or optionally substituted phenyl.