Structure-activity study of cytotoxicity and microtubule assembly in vitro by taxol and related taxanes

Structure-activity relationships of natural and semisynthetic taxanes are reported. Activity is measured in vivo by cytotoxicity toward the macrophage-like cell line J774.2, and in vitro by promotion of microtubule assembly in the absence of exogenous GTP and by inhibition of [³H]taxol binding to microtubule protein. Cytotoxicity and in vitro activity require both an intact taxane ring and ester side chain at position C-13. Addition of acetyl moieties at positions 2′ and 7 results in loss of in vitro activity but not cytotoxicity.