Direct Catalytic Enantioselective Mannich Reactions: Synthesis of Protected anti-α,β-Diamino Acids

Anti-configured protected α,β-diamino acids are prepared with up to 99% ee using a direct catalytic enantioselective Mannich reaction. A catalyst system incorporating a chiral bis (oxazoline) ligand, Mg(ClO 4 ) 2 and Hünigs base, promotes the addition of an isothiocyanate-substituted imide to a variety of aryl-, heteroaryl-, alkenyl-, and alkyl-derived imines. Conversion of the products to their i Pr-ester derivatives allows epimerization to the syn -diastereomers.