The present invention relates to compounds of the general formula (I) in which R1, R2, R11 and R12 represent the same or different radicals selected from the group of C1-8-alkyl, C1-8-halogenoalkyl, C3-6-cycloalkyl, aralkyl or aryl, R3, R5, R7, R9, represent the same or different radicals selected from the group of hydrogen or straight-chain C1-5-alkyl or branched C4-7-alkyl which may optionally be substituted by hydroxyl, C1-4-alkoxy, carboxyl  carboxamide,  imidazolyl, indolyl, guanidino, —SH or C1-4-alkylthio, and furthermore represents aryl, aralkyl or heteroarylmethyl which may be substituted by halogen, hydroxyl, C1-4-alkyl, C1-4-alkoxy, nitro or a —NR13R14 group in which R13 and R14 independently from each other represent hydrogen or alkyl or together with the adjoining nitrogen atom forms a 5, 6 or 7-membered ring which is optionally interrupted by O, S or N and which is optionally C1-4-alkyl substituted, R4, R6, R8, R10 represent the same or different radicals selected from the group of hydrogen, straight-chain C1-5-alkyl and represents isopropyl, sec.-butyl, t-butyl, C2-6-alkenyl, C3-7-cycloalkyl, which may optionally be substituted by hydroxyl, C1-4-alkoxy, carboxyl, carboxamide, imidazolyl, indolyl, guanidino, SH or C1-4-alkylthio and represent aryl, aralkyl or heteroarylmethyl which may be substituted by halogen, hydroxyl, C1-4-alkyl, C1-4-alkoxy, and stereoisomers thereof, to processes for their preparation and to their use as endoparasiticides.