Abstract: A compound, or a solvate or a salt thereof, of formula (I): wherein, Ar is an optionally substituted aryl or a C5-7 cycloalkdienyl group, or a C5-7 cycloalkyl group or an optionally substituted single or fused ring aromatic heterocyclic group; R is C1-6 alkyl, C3-7 cycloalkyl, C3-7 cycloalkylalkyl, optionally substituted phenyl or phenyl C1-6 alkyl, an optionally substituted five-membered heteroaromatic ring comprising up to four heteroatoms selected from O and N, hydroxy C1-6 alkyl, amino C1-6 alkyl, C1-6 alkylaminoalkyl, di C1-6 alkylaminoalkyl, C1-6 acylaminoalkyl, C1-6 alkoxyalkyl, C1-6 alkylcarbonyl, carboxy, C1-6 alkoxycarbonyl, C1-6 alkoxycarbonyl C1-6 alkyl, aminocarbonyl, C1-6 alkylaminocarbonyl, di C1-6 alkylaminocarbonyl, halogeno C1-6 alkyl; or R is a group —(CH2)p— wherein p is 2 or 3 which group forms a ring with a carbon atom of Ar; R1 represents hydrogen or up to four optional substituents selected from the list consisting of: C1-6 alkyl, C1-6 alkenyl, aryl, C1-6 alkoxy, hydroxy, halo