Chemical Dynamic Thermodynamic Resolution and S/R Interconversion of Unprotected Unnatural Tailor-made α-Amino Acids

Described here is an advanced, general method for purely chemical dynamic thermodynamic resolution and S/R interconversion of unprotected tailor-made alpha-amino acids (alpha-AAs) through intermediate formation of the corresponding nickel(11)-chelated Schiff bases. The method features virtually complete stereochemical outcome, broad substrate generality (35 examples), and operationally convenient conditions allowing for large-scale preparation of the target alpha-AAs in enantiomerically pure form. Furthermore, the new type of nonracemizable axially chiral ligands can be quantitatively recycled and reused, rendering the whole process economically and synthetically attractive.