Chiral phosphoric acid-catalyzed chemo and enantioselective 1,2-addition of isatin-derived β,γ-unsaturated α-ketoesters with 4-aminoindoles at the C7 position

Abstract

A protocol for the highly chemo and enantioselective 1,2-addition of isatin-derived β,γ-unsaturated α-ketoesters with 4-aminoindoles at the C7 position has been described, this process was efficiently catalyzed by a SPINOL-derived chiral phosphoric acid to afford the corresponding bisindole derivatives bearing a quaternary stereogenic center in 40–90% yields with up to 97% ee. Further biological study revealed that the products showed high in vitro cytotoxicity (IC₅₀ < 10 μM in most cases) towards A549, HCT116, HeLa, and KSYE150 cancer cell lines.