res: -in which R4 represents a C1-C4 alkyl radical that may be substituted with a hydroxyl radical; wherein: -R5 represents a hydrogen atom, a C-1-C4 alkoxy radical or a halogen atom such as bromine, chlorine, iodine or fluorine, R6 represents a hydrogen atom or a Ci-C4 alkyl radical or forms, with a carbon atom of the benzene ring, a heterocycle that is optionally oxygenous and/or substituted wit