Chiral Borane–Amine Adducts in Asymmetric Synthesis: Alkylation of Alanine Derivatives

Enantiomeric excesses of up to 82% are obtained for the α,α-disubstituted products 4 arising from alkylation reactions of borane–amine adducts 2 and 3, which have a chiral nitrogen atom. The structure of diastereomer 2, which can be obtained selectively in the boration of 1, has been established by single-crystal X-ray analysis.