Diversity Oriented Microwave-Assisted Synthesis of (−)-Steganacin Aza-Analogues

A novel microwave-assisted, highly efficient protocol for the synthesis of hitherto unknown aza-analogues of (−)-Steganacin, a naturally occurring bisbenzocyclooctadiene lignan lactone with potent antileukemic and tubulin polymerization inhibitory activity, has been developed. Focused microwave irradiation is demonstrated to be highly beneficial in promoting the three crucial steps of the sequence to effect the final ring closure: the Suzuki−Miyaura reaction, Cu-mediated A₃-coupling, as well as the intramolecular Huisgen 1,3-dipolar cycloaddition.