A compound of formula II: ** (See formula) ** or a pharmaceutically acceptable salt, solvate or polymorphic form thereof； wherein: R5 is an unsubstituted phenylene group or a phenylene group substituted by one or more groups independently selected from alkyl, halo, alkoxy and haloalkyl； R6 is selected from R7 and R8 are independently selected from the group consisting of hydrogen, optionally substituted C1-6 alkyl and optionally substituted C3-7 cycloalkyl； and X is oxygen； wherein the term "alkyl" refers to saturated straight or branched chain hydrocarbon radicals having 1 to 6 carbon atoms and wherein the term "halo" refers to fluorine, chlorine, bromine and iodine and where the term "alkoxy" refers to straight or branched chain alkyloxy groups, wherein alkyl is as defined above and wherein the expression "optionally substituted" means that the group to which said expression refers may be unsubstituted or may be substituted. with one or more groups independently selected from halogen, C1-C6 alkyl, C2-C6 alkenyl, C1-C6 haloalkyl, C1-C6 alkoxy, hydroxy (C1-6), C3-C6 cycloalkyl, C (O) H, C ( O) OH, NHC (O) H, NHC (O) C1-C4 alkyl, C (O) C1-C4 alkyl, NH2, NH C1-C4 alkyl, N (C1-C4 alkyl) 2, NO2, OH and CN.Un compuesto de fórmula II: **(Ver fórmula)** o una sal, solvato o forma polimórfica farmacéuticamente aceptable del mismo； en donde: R5 es un grupo fenileno sin sustituir o un grupo fenileno sustituido por uno o más grupos seleccionados independientemente entre alquilo, halo, alcoxi y haloalquilo； R6 se selecciona entre R7 y R8 se seleccionan independientemente entre el grupo que consiste en hidrógeno, alquilo C1-6 opcionalmente sustituido y cicloalquilo C3-7 opcionalmente sustituido； y X es oxígeno； en donde el término "alquilo" se refiere a radicales hidrocarburo saturados de cadena lineal o ramificada que tienen de 1 a 6 átomos de carbono y en donde el término "halo" se refiere a flúor, cloro, bromo y yodo y en donde el término "alcoxi" se refiere a grupos alquilox
