A compound having the structural Formula Ia: ** Formula ** or a pharmaceutically acceptable salt thereof, in which: Z is ** Formula ** R1 is ** Formula ** in which *** indicates a binding to the carbonyl carbon and ** indicates the binding to the tetrazolyl ring in Formula Ia； X is O, NH or S； m is an integer selected from 1 or 2； n is an integer selected from 1 or 2； each of X1, X2 and X3 is independently selected from C (R7) or N, with the proviso that at least one of X1, X2 and X3 must be N and at most two of X1, X2 and X3 are N； Ra is -CN； Rb is -H or -C 1-6 alkyl； R2 is -H, -F, -Cl, -C1-6alkyl, -C3-6cycloalkyl or -C1-6alkyl； R3 is -H, -F, -Cl, -CN, -C1-6alkyl, -C3-6cycloalkyl or -C1-6alkyl； R4 is -F, -Cl, -CN, -C1-6alkyl, -C3-6cycloalkyl, -C1-4alkyl or N-tetrazolyl； or R3 and R4 are coupled together with the carbon atoms in the phenyl ring to which they are attached to form: in which R is -H or -C 1-4 alkyl； R5 is -H, -Cl, -F, -CN, -C1-4alkyl, -C3-6cycloalkyl or -C1-4alkyl； with the proviso that when R3 and R4 are not linked together, then one, and only one of R3, R4 or R5 is -CN； R6 is -H or -C 1-4 alkyl； and R7 is -H, -F, -Cl or -C 1-4 alkyl.Un compuesto que tiene la Formula estructural Ia:**Fórmula** o una sal farmaceuticamente aceptable del mismo, en la que: Z es**Fórmula** R1 es**Fórmula** en la que *** indica una union al carbono del carbonilo y ** indica la union al anillo tetrazolilo en la Formula Ia； X es O, NH o S； m es un numero entero seleccionado entre 1 o 2； n es un numero entero seleccionado entre 1 o 2； cada uno de X1, X2 y X3 se selecciona independientemente entre C(R7) o N, con la condicion de que al menos uno de X1, X2 y X3 deba ser N y como mucho dos de X1, X2 y X3 sean N； Ra es -CN； Rb es -H o -alquilo C1-6； R2 es -H, -F, -Cl, -alquilo C1-6, -cicloalquilo C3-6 u -Oalquilo C1-6； R3 es -H, -F, -Cl, -CN, -alquilo C1-6, -cicloalquilo C3-6 u -Oalquilo C1-6； R4 es -F, -Cl, -CN, -alquilo C1-6, -cicloalquilo C3-6, -Oalquilo C1-4 o N-tetrazolilo； o
