en atom, a C1-C4 alkyl radical or forms with a carbon atom of the benzene ring a heterocycle which is optionally oxygen-containing and/or substituted with one or more C1-C4 alkyl groups, R15 represents a hydrogen or halogen atom such as bromine, chlorine, iodine of fluorine, R16 and R17, which are identical or different, represent a hydrogen atom or a C1-C4 alkyl radical, D1 and D2, which are iden