The synthesis and characterization of tetramic acid derivatives as Mdm2-p53 inhibitors

We present syntheses, prediction of tautomer forms and activities of the second generation of the Mdm2-p53 inhibitors that are based on the tetramic acid scaffold. The inhibitors do not contain 6-chloroindole. Binding of these compounds to Mdm2 was checked by two orthogonal methods: the fluorescence polarization and the 1H-15N HSQC NMR titration experiments. We discovered that the 3-phenylthio-substituted tetramic acid derivatives exist in solution solely in their enol forms which is in contrast to the similar 3-aliphatic substituted derivatives. The inhibitory (Ki) and dissociation (KD) constants are in low micromolar ranges with the best binding compound 9a having KD = 2.9 μM. Furthermore, our data show that the compounds indeed bind to the p53-binding pocket of Mdm2 and do not cause dimerization of Mdm2. The current work provides solid base for further rational design of the Mdm2/p53 inhibitors.