Asymmetric construction of polycyclic indole derivatives with different ring connectivities by an organocatalysis triggered two-step sequence

Abstract

An organocatalysis triggered highly regio- and stereoselective two-step sequence between hemiacetals and indole-containing nitroolefins was developed. The key to the success of this sequence was the intramolecular oxocarbenium ion induced collective alkylation at the C3, C2, or N1-position of the indole moiety, respectively, providing biologically important polycyclic indole derivatives with different ring connectivities. An unexpected epimerization was observed during the C3-alkylation process, which generated products with different relative configurations compared with the C2- and N1-alkylation products.