A Convenient Route to Enantiopure 3-Aryl-2,3-diaminopropanoic Acids by Diastereoselective Mannich Reaction of Camphor-Based Tricyclic Iminolactone with Imines

A novel and convenient route to the asymmetric synthesis of 2,3-diamino acids via Mannich reaction of iminolactones 1a and 1b with N-protected imines has been achieved in good yields (up to 95%) and high diastereoselectivity (dr: >99:1). Hydrolysis of the Mannich adducts under acidic conditions furnished the desired 3-aryl-2,3-diaminopropanoic acids in good yields (up to 85%) with excellent enantiomeric excesses (99% ee).