Chemical Dynamic Thermodynamic
Resolution and <i>S</i>/<i>R</i> Interconversion
of Unprotected Unnatural
Tailor-made α‑Amino Acids
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Abstract
Described
here is an advanced, general method for purely chemical
dynamic thermodynamic resolution and <i>S</i>/<i>R</i> interconversion of unprotected tailor-made α-amino acids (α-AAs)
through intermediate formation of the corresponding nickel(II)-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 α-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