Chemical Dynamic Kinetic Resolution and S/R Interconversion of Unprotected α‐Amino Acids

Abstract

Reported herein is the first purely chemical method for the dynamic kinetic resolution (DKR) of unprotected racemic α-amino acids (α-AAs), a method which can rival the economic efficiency of the enzymatic reactions. The DKR reaction principle can be readily applied for S/R interconversions of α-AAs, the methodological versatility of which is unmatched by biocatalytic approaches. The presented process features a virtually complete stereochemical outcome, fully recyclable source of chirality, and operationally simple and convenient reaction conditions, thus allowing its ready scalability. A quite unique and novel mode of the thermodynamic control over the stereochemical outcome, including an exciting interplay between axial, helical, and central elements of chirality is proposed.

Rational Design and Synthesis of Modified Teixobactin Analogues: In Vitro Antibacterial Activity against Staphylococcus aureus, Propionibacterium acnes and Pseudomonas aeruginosa

“…It has been shown in other studies that when am onoalkylated complex is subjected to epimerisation under basic conditions, thermodynamic control would dominate and eventually drives the equilibrium towards the favoured (S,S) epimer. [46][47][48] Thus, am ixture of the (S,S)-and (S,R)-alkylated complex 6 was partially purified in ar eactionworkup,and subsequently treated with K 2 CO 3 in MeOH at 60 8C( Ta ble 1, entry 3). As atisfactory diastereomeric ratio of 97:3 was obtained.…”

Which Stereoinductor Is Better for Asymmetric Functionalization of α‐Amino Acids in a Nickel(II) Coordination Environment? Experimental and DFT Considerations

“…Later, this design was profoundly improved by introducing a new generation of tridentate ligands that possessed various elements of chirality (stereogenic center, stereogenic center in combination with axial chirality, etc. ) Chemical modification of the chiral ligand sphere by insertion of bulky electron‐donating or ‐withdrawing substituents was also tested to provide various stereoselectivity levels . To provide a rationale for variations in the stereoselectivity level, as well as for developing and molecular engineering of new chiral materials, elucidation of possible mechanisms that determine the relationship between the steric configuration of a molecule and its electronic structure will be helpful.…”

Large‐Scale Asymmetric Synthesis of Fmoc‐(S)‐2‐Amino‐6,6,6‐Trifluorohexanoic Acid

“…[16] Using the modular design for the chiral tridentate ligands, [17] we explored various structural ideas, featuring NÀ H functionality [18] as well as elements helical chirality. [19] One of the most recent developments is a tri-chloro-substituted ligand 4 (Scheme 2) rationally optimized to increase its stereocontrolling properties. [20] So far, this new ligand was quite successfully used for the dynamic kinetic resolution of unprotected α- [21] and β-AAs.…”