Axially chiral Ni(II) complexes of α-amino acids: Separation of enantiomers and kinetics of racemization

Wenzhong Zhang (1) , Romuald Eto Ekomo (2) , Christian Roussel (2) , Hiroki Moriwaki (3) , Hidenori Abe (3) , Han Jianlin (1) , Vadim A. Soloshonok (4, 5)

1 NJU - Nanjing University
2 ISM2 - Institut des Sciences Moléculaires de Marseille
3 Hamari Chemicals
4 UPV / EHU - University of the Basque Country = Euskal Herriko Unibertsitatea
5 Ikerbasque - Basque Foundation for Science

Herein we present design, synthesis, chiral HPLC resolution, and kinetics of racemization of axially chiral Ni(II) complexes of glycine and di-(benzyl)glycine Schiff bases. We found that while the ortho-fluoro derivatives are configuration-ally unstable, the pure enantiomers of corresponding axially chiral ortho-chloro-containing complexes can be isolated by preparative HPLC and show exceptional configurational stability (t 1/2 from 4 to 216 centuries) at ambient conditions. Synthetic implications of this discovery for the development of new generation of axially chiral auxiliaries, useful for general asymmetric synthesis of α-amino acids, are discussed.

Mots clés: amino acids; axial chirality; chiral HPLC; kinetic of racemization; rotational energy barriers

Domaines: Chimie

Wenzhong Zhang, Romuald Eto Ekomo, Christian Roussel, Hiroki Moriwaki, Hidenori Abe, et al.. Axially chiral Ni(II) complexes of α-amino acids: Separation of enantiomers and kinetics of racemization. Chirality, 2018, 30 (4), pp.498-508. ⟨10.1002/chir.22815⟩. ⟨hal-02093234⟩