Asymmetric organocatalyzed Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde and the three one-pot sequential synthesis of (-)-horsfiline and (-)-coerulescine.

Abstract

(-)-Horsfiline and (-)-coerulescine were synthesized through three one-pot operations in 33 and 46% overall yield, respectively. Key to the success was the efficient use of a diarylprolinol silyl ether to catalyze the asymmetric Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde. This allowed the all-carbon quaternary, spirocyclic carbon stereocenter to be constructed in good yield with excellent enantioselectivity.