Taccalonolides are plant-derived steroids which act as microtubule poisons on mammalian cells with a taxol-like mechanism. This makes them potentially useful lead compounds for thedevelopment of anti-cancer agents specifically breast cancer. Natural taccalonolide A was modified through selective chemical reactions at various sites in the molecule in preparation for biological tests that will compare the biological effects and potency of the derivatives with that of the starting material. These studies ...