Acid derivative pyrrolidin-3-ylacetic

A compound represented by formula (1) or a pharmaceutically acceptable salt thereof: Formula ** ** wherein R represents a C1-6 alkyl unsubstituted or having 1 to 3 substituents selected from halogen atoms, C3-8 cycloalkyl group unsubstituted or having 1 to 3 substituents selected from halogen atoms, or a cycloalkenyl group C3-8 unsubstituted or having 1 to 3 substituents selected from halogen atoms, X represents a C1-6 alkyl group, Y and Z are the same or different, and each represents a halogen atom or an C1-6 alkyl group unsubstituted or having 1 to 3 substituents selected from halogen atoms, n It represents 0 or 1.