a hydrogen atom, a halogen atom, in particular a chlorine atom, a C1-C6 alkyl group optionally substituted with a hydroxyl or C1-C6 alkoxy group, a C1-C6 alkoxy group, a (C1-C6)alkylcarbonylamino group; an amino group, an amino(C1-C6)alkylcarbonylamino group, an aminocarbonylamino group, a (C1-C6)alkoxycarbonylamino group (C1-C4 aminoesteralkyl), an aminocarbonyl group in which the amino group may