<i>Syn</i>-Selective Synthesis of β‑Branched α‑Amino Acids by Alkylation of Glycine-Derived Imines with Secondary Sulfonates

A <i>syn</i>-selective synthesis of β-branched α-amino acids has been developed based on the alkylation of glycine imine esters with secondary sulfonates. The potassium counterion for the enolate, the solvent, and the leaving group on the electrophile were key levers to maximize the diasteroselectivity of the alkylation. The optimized conditions enabled a straightforward preparation of a number of β-branched α-amino acids that can be challenging to obtain