Organocatalytic Asymmetric Mannich Reactions of 5H-Oxazol-4-ones: Highly Enantio- and Diastereoselective Synthesis of Chiral α-Alkylisoserine Derivatives

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 Mannich adducts, important -methyl--hydroxy--amino acid derivatives, such as the -methylated C-13 side chain of taxol and taxotere, can be conveniently prepared.