A Biomimetic Route for Construction of the [4+2] and [3+2] Core Skeletons of Dimeric Pyrrole–Imidazole Alkaloids and Asymmetric Synthesis of Ageliferins

The pyrrole–imidazole alkaloids have fascinated
chemists
for decades because of their unique structures. The high nitrogen
and halogen contents and the densely functionalized skeletons make
their laboratory synthesis challenging. We describe herein an oxidative
method for accessing the core skeletons of two classes of pyrrole–imidazole
dimers. This synthetic strategy was inspired by the putative biosynthesis
pathways and its development was facilitated by computational studies.
Using this method, we have successfully prepared ageliferin, bromoageliferin,
and dibromoageliferin in their natural enantiomeric form.