roxyalkyl radicals, (C1-C4)alkoxy(C1-C4)alkyl radicals and C1-C4 alkyl radicals substituted with at least one nitrogen-containing radical; [0154] R7 is chosen from a hydrogen atom, halogen atoms such as a chlorine atom, a bromine atom, an iodine atom and a fluorine atom, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C1-C4 hydroxyalkoxy radicals, acetylamino(C1-C4)alkoxy radicals, mesylami