Efficient relay syntheses and assessment of the DNA-cleaving properties of the pyrrole alkaloid derivatives permethyl storniamide A, lycogalic acid A dimethyl ester, and the halitulin core

Palladium catalyzed Suzuki- and Negishi cross coupling reactions are used to convert the now readily available 3,4-dibromopyrrole derivatives and into the core structures of different pyrrole alkaloids. Several compounds of this series exhibit respectable cytotoxicity and resensitize multidrug resistant (MDR) cancer cell lines at non-toxic concentrations. Cytotoxicity and MDR reversal can be efficiently uncoupled by per-O-methylation of the peripheral hydroxyl groups. For the storniamide core structure it is demonstrated that this chemical modification goes hand in hand with a complete loss of the DNA-cleaving capacity of the alkaloid.