Thiourea-Catalyzed Enantioselective Addition of Indoles to Pyrones: Alkaloid Cores with Quaternary Carbons

We report the development
of a catalytic method for the enantioselective
addition of indoles to pyrone-derived electrophiles. Arylpyrrolidino-derived
thioureas catalyze the addition with high stereoselectivity in the
presence of catalytic quantities of an achiral Brønsted acid.
The indole–pyrone adducts feature a quaternary stereocenter
and represent an unusual class of indolines bearing structural resemblance
to the hybrid natural product pleiocarpamine.