The invention relates to compounds of general formula (I), where R1 and R2 are independently selected from a hydrogen atom, a branched or straight chain alkyl with 1 to 6 carbon atoms, a fluoroalkyl group with 1 to 6 carbon atoms and 3 to 7 fluorine atoms, A is an aromatic group with one or several rings, optionally comprising one or more heteroatoms and B is an optionally-substituted phenyl group, or an optionally-substituted pyridine.