Synthesis and biological activities of new conformationally fixed analogues of (−)-indolactam-V, the core structure of tumor-promoting teleocidins

Abstract (−)-Indolactam-V ( 1 ) exists as two stable conformers, the twist and the sofa form, in solution at room temperature. 3-Aza-Cope rearrangement of (−)- N 13 -desmethyl- N 13 -allylindolactam-V ( 5 ) gave new conformationally restricted analogues ( 2a and 3 ) along with a normal rearrangement product ( 7 ). Both 2a and 3 , whose fixed conformation was the twist form, showed significant biological activities related to tumor promotion.