Asymmetric C–C Bond Formation between Chiral N ‐Phosphonyl Imines and a Nickel(II)‐Complexed Glycine Schiff Base Provides Efficient Synthesis of α,β‐ syn ‐Diamino Acid Derivatives

The group‐assisted purification asymmetric synthesis of α,β‐diamino acid derivatives was achieved by treating chiral N ‐phosphonyl imines with a Ni II ‐complexed glycine‐derived enolate; traditional purification techniques such as chromatography and recrystallization are not required. Successful control of the syn stereochemistry of the vicinal diamino products complements our previous methods that afforded anti stereoisomers; thus, all four individual isomers can be synthesized simply by changing the geometry of the enolate. In contrast to our previous synthesis in which at least 5 equiv. of the glycine Schiff base enolate was required for complete conversion, the new synthesis only needs 1.1 equiv. of the glycine Schiff base enolate to give complete diastereoselectivity (>30:1  dr ) and high yields (91–97 %). The absolute stereochemistry was unambiguously determined by X‐ray structure analysis.