Radanamycin, a macrocyclic chimera of radicicol and geldanamycin.

Radicicol and geldanamycin are potent inhibitors of the Hsp90 protein folding machinery, which is an emerging target for the development of cancer chemotherapeutics. However, radicicol is inactive in vivo and geldanamycin suffers from its redox-active behavior that produces toxicity unrelated to Hsp90 inhibition. It was proposed that a chimeric molecule containing the resorcinol ring of radicicol and the quinone of geldanamycin could provide an opportunity to elucidate structure-activity relationships for both natural products and serve as a starting point for the development of more potent inhibitors. Synthesis of the macrocyclic chimera named radanamycin is reported along with the biological activity exhibited by this compound in MCF-7 breast cancer cells.