The present invention relates to compounds of the general formula (I) ##STR1## in which R.sup.1 and R.sup.12 represent the same or different radicals selected from the group of C.sub.2-9 -alkyl, C.sub.1-8 -halogeno-alkyl, C.sub.3-6 -cycloalkyl, aralkyl or aryl, R.sup.3 to R.sup.10 represent the same or different radicals selected from the group of hydrogen, C.sub.1-5 -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 --NR.sup.13 R.sup.14 group in which R.sup.13 or R.sup.14 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 C.sub.1-4 -alkyl, R.sup.2 and R.sup.11 represent the same of different radicals selected from the group of C.sub.1-4 -alkyl, and stereoisomers thereof, to processes for their preparation and to their use as endoparasiticides.