A compound of formula (I): wherein A1 represents 2,3-dihydro-1-benzofuran-7-yl, 5-fluoro-2-methoxy-phenyl or 5-fluoro-2-hydroxy-phenyl; X represents —C(R3)— or nitrogen; when X represents —C(R3)—, R2 represents hydrogen and R1 represents fluorine, R3 represents hydrogen or fluorine, when X represents —C(R3)— and R2 and R1 each represent hydrogen, R3 represents hydrogen, hydroxy, methoxy or fluorine, when X represents —C(R3)— and R2 represents hydroxy, methoxy, —CO2CH3 or —CO2CH2CH3, R1 and R3 each represent hydrogen, when X represents nitrogen, R1 and R2 each represent hydrogen; and Y represents H or methyl; or a physiologically functional derivative thereof.