The present invention relates to compounds of the general formula (I) in which R1 and R12 represent the same or different radicals selected from the group of C2-9-alkyl, C1-8-halogen-alkyl, C3-6-cycloalkyl, aralkyl or aryl, R3 to R10 represent the same or different radicals selected from the group of hydrogen, C1-5-alkyl which may optionally be substituted by hydroxyl, alkoxy, carboxyl, carboxamide, imidazolyl, indolyl, guanidino, thio- or thioalkyl, and represent aryl, alkylaryl or heteroarylmethyl which are optionally substituted by halogen, hydroxyl, alkyl, alkoxy, nitro or a —NR13R14 group in which R13 or R14 independently from each other represent hydrogen or alkyl or together with the adjoining nitrogen atom form a 5, 6 or 7-membered ring which is optionally interrupted by O, S or N and which is optionally substituted by C1-4-alkyl, R2 and R11 represent the same of different radicals selected from the group of C1-4-alkyl, and stereoisomers thereof, to processes for their preparation and to their use as endoparasiticides.