Stereoselective alkylation of aldimines, prepared from α-amino esters and pyridoxal models having an ionophoric side-chain composed of a chiral glycerol structure, proceeded in the presence of Li+or Na+to afford α,α-dialkyl amino esters after acidic hydrolysis. Both the structure of the side chain and the metal ion were found to be in relation with the stereoselectivity, affording the highest stereoselectivity when the side- chain having a 2-naphthylmethoxy group and a methoxy group at the respective 3'- and 2'-positions was employed in the presence of Na+.
Miyashita, K., Miyabe, H., Tai, K., Kurozumi, C., Iwaki, H., & Imanishi, T. (1999). Chiral environment specifically induced by metal ion: Asymmetric α- alkylation of α-amino esters using pyridoxal derivatives having a chiral ionophore function. Tetrahedron, 55(41), 12109–12124. https://doi.org/10.1016/S0040-4020(99)00708-5