A compound represented by formula (I): ##STR1## wherein R.sub.1 represents a halogen atom, a lower alkyl group, a lower alkoxy group, a hydroxyl group, a nitro group, a trifluoromethyl group, a lower alkylthio group, an acyl group, a carboxyl group, a mercapto group or an amino group; R.sub.2 represents a hydrogen atom, a lower alkyl group, a lower alkenyl group, a lower alkynyl group, an alkoxy group, an acyl group, an aryl group or a heterocyclic group; R.sub.3 represents a lower alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group; R.sub.4 represents a hydrogen atom, a lower alkyl group, an aryl group, a heterocyclic group, --OR.sub.5, --SR.sub.5 or --NR.sub.6 R.sub.7 (wherein R.sub.5, R.sub.6, and R.sub.7 each represent a lower alkyl group, etc.); X and Y each represent --CH.sub.2 --, --NH-- or --O--; and n represents an integer of from 0 to 4, and an intermediate for synthesis thereof are disclosed. The compound of the present invention exhibits selective antagonism against gastrin receptors without causing side effects attributed to CCK-A receptor antagonism and is useful for the treatment and prevention of peptic ulcers, gastritis, reflux esophagitis, and Zollinger-Ellison syndrome, and for the treatment of neoplasm originating in the gastrointestinal system.