ASYMMETRIC TITANIUM-CATALYZED MICHAEL ADDITION OF O-BENZYLHYDROXYLAMINE TO ALPHA,BETA-UNSATURATED CARBONYL-COMPOUNDS - SYNTHESIS OF BETA-AMINO ACID PRECURSORS

A new titanium-catalysed Michael type addition of O-benzylhydroxylamin e to alpha,beta-unsaturated N-acylated 1,3-oxazolidinones giving beta- amino acid precursors has been developed. The reaction is catalysed by TiX(2)-TADDOLate and TiCl2-BINOLate complexes and good conversions wi th enantiomeric excesses up to 42% were obtained with the application of 10 mol% of the catalyst. In order to determine the absolute stereoc hemistry of the enriched enantiomer one of the products, 3-(3-benzylox yaminobutanoyl)-1,3-oxazolidin-2 was converted into methyl 3-benzoylam inobutanoate. Based on the absolute stereochemistry of the Michael typ e addition product the mechanism for the addition step is discussed, a s well as the structure of the active intermediate.