Enzymatic Synthesis of Unprotected alpha , beta-Diamino Acids via Direct Asymmetric Mannich Reactions.
Liu, S., Gao, J., Zou, Y., Hai, Y.(2024) J Am Chem Soc 146: 20263-20269
- PubMed: 39001849 
- DOI: https://doi.org/10.1021/jacs.4c05581
- Primary Citation of Related Structures:  
9AZA, 9AZB - PubMed Abstract: 
α,β-Diamino acids are important structural motifs and building blocks for numerous bioactive natural products, peptidomimetics, and pharmaceuticals, yet efficient asymmetric synthesis to access these stereoarrays remains a challenge. Herein, we report the development of a pyridoxal 5'-phosphate (PLP)-dependent enzyme that is engineered to catalyze stereoselective Mannich-type reactions between free α-amino acids and enolizable cyclic imines. This biocatalyst enabled one-step asymmetric enzymatic synthesis of the unusual pyrrolidine-containing amino acid L-tambroline at gram-scale with high enantio- and diastereocontrol. Furthermore, this enzymatic platform is capable of utilizing a diverse range of α-amino acids as the Mannich donor and various cyclic imines as the acceptor. By coupling with different imine-generating enzymes, we established versatile biocatalytic cascades and demonstrated a general, concise, versatile, and atom-economic approach to access unprotected α,β-diamino acids, including structurally complex α,α-disubstituted α,β-diamino acids with contiguous stereocenters.
Organizational Affiliation: 
Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States.