The diazatricyclic core of the madangamine alkaloids was synthesized from a densely functionalized cyclohexane derivative. An alkene and two cyanoformamide groups are used to form two new rings and a new quaternary stereocenter in a cascade reaction, which involves two Pd-catalyzed C-C bond activation steps. The synthesis of the cascade precursor involves an intramolecular Staudinger reaction of a vicinal diester that gives a [3.2.1]azabicyclooctane derivative, allowing the regioselective introduction of a monosubstituted alkene.
Bibliographical noteFunding Information:
We thank the National Institutes of Health (R01 GM095559) for funding this work. We also thank Dr. Letitia Yao (UMN) for assistance with 2D NMR experiments and Prof. Daniel Everson (CSU Chico) for preliminary studies into the synthesis of 4 .