Aminophenol derivatives represented by the following formula (1): ##STR1## wherein X is O or S; A is alkylene, R.sup.1 is phenyl, etc., R.sup.2 and R.sup.3 are H or alkyl; R.sup.4 is substituted carbamoylalkyl, etc.; R.sup.5 is substituted amino, etc.; their salts, and optical isomers of the derivatives and salts. Also disclosed are gastrin receptor antagonists, cholecystokinin receptor antagonists, and medicines for digestive diseases. The compounds have strong binding inhibition against gastrin receptor or CCK-A receptor and also they have higher selectivity to either group of CCK-A receptor or gastrin receptor, and therefore, the compounds are useful for preventing and treating gastrointestinal diseases including peptic ulcers as well as central nervous system diseases.