Synthesis of new 6-(4-chlorophenyl)perhydro-1,3-diazepine-2,4-diones was accomplished starting from 4-amino-3-(4-chlorophenyl)butyricacid (Baclofen). The chemical pathway involved the cyclisation of various 3-(4-chlorophenyl)-4-ureidobutyric acids. However, none of the new derivatives retained the anticonvulsant activity of their six-membered ring homologues, belonging to the phenylpyrimidinedione