Stereodivergent Synthesis of α,α-Disubstituted α‑Amino Acids via Synergistic Cu/Ir Catalysis

Cu/Ir dual catalysis has been developed
for the stereodivergent
α-allylation of aldimine esters. The method enables the preparation
of a series of nonproteinogenic α-amino acids (α-AAs)
bearing two contiguous stereogenic centers in high yield with excellent
stereoselectivity. All four product stereoisomers could be obtained
from the same set of starting materials via pairwise combination of
two chiral catalysts. Notably, one-pot protocol could be successfully
applied for the preparation of the bimetallic Cu/Ir complexes to simplify
the manipulation of Cu/Ir dual catalysis. This method could be further
utilized for the construction of the key intermediate of a bioactive
pyrrolidine derivative and the concise synthesis of a plant growth
regulator (2S,3S)-2-amino-3-cyclopropylbutanoic
acid.