Asymmetric Synthesis of Chiral alpha-Methyl-alpha,beta-diamino Acid Derivatives via Group-Assisted Purification Chemistry Using N-Phosphonyl Imines and a Ni(II)-Complexed Alanine Schiff Base

摘要

The Mannich reaction between chiral N-phosphonyl imines and a Ni(II)-complexed alanine Schiff base (Ala-Ni) is reported. With a chiral phosphonyl auxiliary, a single isomer of alpha-methyl-alpha,beta-diamino acid derivative containing vicinal chiral centers, including a chiral quaternary carbon center, can be obtained simply by washing the crude mixture with cosolvents. The absolute stereochemistry of the enantiomerically pure product has been unambiguously determined by X-ray crystallographic analysis.