4-(3,4-Dichlorophenyl)-9-(4-methyl- phenylsulfonyl)-4,9-diazatetracyclo- [5.3.1.0.0]undecane-3,5-dione and 4-(4-chlorophenyl)-9-(4-methyl- phenylsulfonyl)-4,9-diazatetracyclo- [5.3.1.0.0]undecane-3,5-dione

Maleimides and aziridines are well known for the diversity of their applications in medicinal chemistry. A great number of compounds with an aziridine ring have been synthesized, many of which have shown signi®cant cytotoxicity against some tumour cells, such as mitomycin C, which is a bioreductive alkylating agent used in anticancer therapy (Kim et al., 1996; Kumar et al., 1996). Maleimides have also shown activity against some types of tumour, together with other pharmacological properties such as sedative, hypnotic, antihypertensive and diuretic properties, and in chemotherapy for tuberculosis. An example of a useful maleimide is mitona®de, which is already used as a drug and which has also been used as a model in the development of new drugs with improved effectiveness and reduced adverse effects (Asbury et al., 1994; Cechinel Filho et al., 2003).