Catalytic Asymmetric Synthesis of Unnatural Axially Chiral Biaryl δ‐Amino Acid Derivatives via a Chiral Phenanthroline‐Potassium Catalyst‐Enabled Dynamic Kinetic Resolution
Shouyi Cen, Shanshan Li, Yin Zhao, Mei‐Xin Zhao, Zhipeng Zhang
Abstract
Axially chiral biaryl δ-amino acids possess significantly different conformational properties and chiral environment from centrally chiral amino acids, therefore, have drawn considerable attention in the fields of synthetic and medicinal chemistry. Herein, a novel chiral phenanthroline-potassium catalyst has been developed by constructing a well-organized axially chiral ligand composed of one 1,10-phenanthroline unit and two axially chiral 1,1'-bi-2-naphthol (BINOL) units. In the presence of this catalyst, good to excellent yields and enantioselectivities (up to 99 % yield, 98 : 2 er) have been achieved in the ring-opening alcoholytic dynamic kinetic resolution of a variety of biaryl lactams, thereby providing an efficient protocol for catalytic asymmetric synthesis of unnatural axially chiral biaryl δ-amino acid derivatives.