A compound of the formula I: ** Formula ** or a pharmaceutically or veterinarily acceptable salt thereof, or a pharmaceutically or veterinarily acceptable solvate thereof, wherein: R1 and R3 each independently represents, at each occurrence when used herein. , H or C1 to C6 alkyl； R2 represents halo； R4 and R5 each independently represents H； R6 represents -C (O) OR9； X represents O or S； R9 represents H or C1 to C6 alkyl； and, m is an integer from 1 to 6 inclusive.Un compuesto de la fórmula I:**Fórmula** o una sal farmacéuticamente o veterinariamente aceptable del mismo, o un solvato farmacéuticamente o veterinariamente aceptable del mismo, en donde: R1 y R3 cada uno representa independientemente, en cada ocurrencia cuando se utiliza aquí, H o alquilo C1 a C6； R2 representa halo； R4 y R5 cada uno representa independientemente H； R6 representa -C(O)OR9； X representa O o S； R9 representa H o alquilo C1 a C6； y, m es un entero de 1 a 6 inclusive.
