Potent Cytotoxic Analogs of Amphidinolides from the Atlantic Octocoral .

Amphidinolides are cytotoxic macrolides produced by symbiotic unicellular microalgae of the genus . Here we describe the identification of four related molecules belonging to this macrolide family isolated from the invertebrate . The new molecules, named amphidinolide PX1-PX3 and stragulin A (⁻), show an unprecedented carbon skeleton whose complete stereochemistry has been determined by spectroscopic and computational methods. Differences in the structures of these molecules modulate their biological activity in a panel of tumor cell lines, but the opened derivative stragulin () shows a very potent and specific cytotoxic activity (IC 0.18 µM) against the aggressive human melanoma cell A2058.