he compounds corresponding to the following formula (VI): and their addition salts with an acid: wherein, in formula (VI): [00110] -R20 is chosen from a hydrogen atom, a halogen atom, such as fluorine, a C1-C4 alkyl radical, a C1-C4 monohydroxyalkyl radical, a (Ci-C4)alkoxy(Ci-C4) alkyl radical, a C1-C4 aminoalkyl radical or a hydroxy(Ci-C4)alkylamino-( Ci-C4)alkyl radical, and [00111] -R21