A compound with the formula I: ** (See formula) ** and salts and solvates thereof, in which: when there is a simple bond present between C2 and C3, R2 is selected from the group consisting of: (ia ) C5-10 aryl group, optionally substituted with one or more substituents selected from the group comprising: halo, nitro, cyano, ether, C1-7 alkyl, C3-7 heterocyclyl and bis-oxy-C1-3 alkylene； (ib) saturated aliphatic C1-5 alkyl； (ic) saturated C3-6 cycloalkyl； (id) wherein each of R11, R12 and R13 are independently selected from H, saturated C1-3 alkyl, C2-3 alkenyl, C2-3 alkynyl and cyclopropyl, where the total number of carbon atoms in the group R2 20 it is not more than 5； (ie) ** (See formula) ** in which one of R15a and R15b is H and the other is selected from: phenyl, phenyl which is optionally substituted by a group selected from halo, methyl, methoxy pyridyl and thiophenyl； and (if) ** (See formula) ** in which R14 is selected from: H； saturated C1-3 alkyl； C2-3 alkenyl； C2-3 alkynyl； cyclopropyl； phenyl, phenyl which is optionally substituted with a group selected from halo, methyl, methoxy, pyridyl and thiophenyl； when there is a simple link present between C2 and C3, R2 35 is ** (See formula) ** ...Un compuesto con la fórmula I: **(Ver fórmula)** y sales y solvatos de los mismos, en la que: cuando hay un enlace simple presente entre C2 y C3, R2 se selecciona entre el grupo que consiste en: (ia) grupo arilo C5-10, sustituido opcionalmente con uno o más sustituyentes seleccionados del grupo que comprende: halo, nitro, ciano, éter, alquilo C1-7, heterociclilo C3-7 y bis-oxi-alquileno -C1-3； (ib) alquilo C1-5 alifático saturado； (ic) cicloalquilo C3-6 saturado； (id) en donde cada uno de R11, R12 y R13 se seleccionan independientemente de H, alquilo C1-3 saturado, alquenilo C2-3, alquinilo C2-3 y ciclopropilo, donde el número total de átomos de carbono en el grupo R2 20 no es más de 5； (ie) **(Ver fórmula)** en la que uno de R15a y R15b es H y el otro se selecciona
