The phenylhydrazone of benzaldehyde (I) is obtained in the usual way, phenylhydrazine (A) with benzaldehyde (B), which by reaction with benzoyl chloride (II) gives (C) and further treatment with HCl in an organic solvent results in the substituted hydrazine hydrochloride (III). Finally, this compound is condensed with levulinic acid (IV) at high temperature.