Abstract
Cytochalasin D (zygosporin A) showed strong cytotoxic effect with a unique cytopathogenic change. Further, cytochalasin D inhibited the growth of several rat tumors in a narrow chemotherapeutic index range owing to its irritating toxicity. More than 30 derivatives of zygosporin were synthesized, and structure-biology relationship was discussed for cytotoxicity and skin irritating activity. Among the derivatives, cytochalasin C has similar cytotoxicity to cytochalasin D, accompanied by a decreased lethal toxicity. It is disappointing, however, that the chemotherapeutic index of cytochalasin C is no different from that of cytochalasin D.