Abstract: Novel oxindole derivative and salt thereof represented by the general formula, ##STR1## wherein R.sup.1 is a hydrogen atom, a lower alkyl group, a lower alkenyl group, a lower alkynyl group or a phenyl-lower alkyl group; R.sup.2 is a hydrogen atom or a lower alkyl group; R.sup.3 is a hydrogen atom, a cycloalkylcarbonyl group, a benzoyl group which may have 1 to 3 substituents selected from the group consisting of a halogen atom, a lower alkyl group and a lower alkoxy group on the phenyl ring, or a phenyl-lower alkanoyl group which may have halogen atoms as the substituents on the phenyl ring; provided that when R.sup.4 is a hydrogen atom, then R.sup.3 should be neither a hydrogen atom nor a lower alkyl group.The novel oxindole derivative and salt thereof possesses anti-peptic ulcer effects and are useful as anti-peptic ulcer agents.

Abstract: Compounds of the formula Ia and Ib ##STR1## are prodrugs of allopurinol and have i.a. a much higher solubility in water and/or a higher lipophilicity than allopurinol, which makes such compounds useful for oral, parenteral and rectal administration to a warm-blooded animal such as a human. Such compounds will after administration be converted into allopurinol.