Abstract The first organocatalytic Mannich reaction of 5H-oxazol-4-ones with various readily prepared aryl-and alkylsulfonimides has been developed. Two commercially available pseudoenantiomeric Cinchona alkaloids-derived tertiary amine/ureas have been demonstrated as the most efficient catalysts to access the opposite enantiomers of the Mannich products with equally excellent enantio-and diastereoselectivities. From the ...