Highly Stereoselective [4+2] Cycloaddition of Azlactones to β,γ‐Unsaturated α‐Ketoesters Catalyzed by an Axially Chiral Guanidine Base

Abstract

Sweet catalysis! The enantio- and diastereoselective cycloaddition reaction of azlactones with β,γ-unsaturated α-ketoesters was demonstrated by taking advantage of the multiple reactive sites on the azlactone with the use of an axially chiral guanidine-base catalyst. The most likely reaction pathway involves three consecutive steps to provide a facile access to α-amino δ-lactones with a sugar framework in a highly stereoselective manner (see scheme).