For the structure-activity-studies, it was necessary to enhance the solubility of the tested compounds. The concentration of the most interesting compound THPC112-subs.PDAPtcis 4 could be enhanced to a nearly complete solubility. The activity of the THPC112-subs.PDAPtcis 4 complexed with mixed micells is slower than that of the free compound, but over all a little bit better. The cytotoxic tests showed that the spacer length of 11 has the best results. It could be proved in this work that not intracellular mechanisms are responsible for this effect, but the better uptake of the compound into the cells compared with cisplatin. For the toxic effect itself, the symmetric connection between the platinum part and the spacer is responsible. The uptake of the compound into the cell is direct propotional to the concentration in the medium and to the incubation time. Concerning the betulinic acid compounds, the knowledge of the literature was found to be correct. For example it was possible to enhance the cytotoxic activity by short esterifications at C3. Reactions at C28 also have a good potential, but this is like the derivatives at C3 limited to a few groups. Only the TRIS-ester is able to enhance the IC50-value. In contrast to the results of the platinum compounds, longer chains and lipophilic groups cause nearly an inactivation of the cytotoxic activity.