Z, X3 is a hydrogen or halogen atom, a C1 -C4 -alkyl or alkoxy radical or a Y or Z radical, Y denotes the ##STR9## group in which R1 is a hydrogen atom or a C1 -C4 -alkyl or hydroxyalkyl radical, R2 is a hydrogen atom or a linear or branched alkyl or alkenyl radical or a cycloalkyl, aryl or aralkyl radical, it being possible for these various C1 -C20 radicals to be substituted by one or more hydro