Biomimetic synthesis of (−)-chaetominine epimers via copper-catalyzed radical cyclization

Synthetic endeavors toward (−)-chaetominine via copper-catalyzed radical cyclization are reported. Both of the pyrido[2,3,b]-indole ring (C ring) and imidazolidinone (D ring) are efficiently constructed in one-pot manner. It's unveiled that the newly formed stereo center is controlled by the chiral of alanine, not by tryptophan. With these synthetic discoveries, highly efficient and diastereoselective synthesis of (+)-2,3,14-epi-chaetominine 5 and (−)-11-epi-chaetominine 11 is achieved.