A hydroquinonylphenyl butyric acid amide derivative having the formula (I):
wherein R¹ represents an aromatic or heterocyclic group which may be substituted, R² represents a hydrogen atom, a lower alkylcarbonyl group, an aromatic carbonyl or heterocyclic carbonyl group which may be substituted, and X represents an oxygen atom or sulfur atom or a pharmaceutically acceptable salt thereof, which has a cerebral insufficiency improving activity.
A hydroquinonylphenyl butyric acid amide derivative having the formula (I): ##STR1## wherein R.sup.1 represents an aromatic or heterocyclic group which may be substituted, R.sup.2 represents a hydrogen atom, a lower alkylcarbonyl group, an aromatic carbonyl or heterocyclic carbonyl group which may be substituted, and X represents an oxygen atom or sulfur atom or a pharmaceutically acceptable salt thereof, which has a cerebral insufficiency improving activity.