Synthesis 2021; 53(16): 2767-2776
DOI: 10.1055/a-1463-4266
short review

In the Pursuit of (Ald)Imine Surrogates for the Direct Asymmetric Synthesis of Non-Proteinogenic α-Amino Acids

a   Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, Florida 33431, USA
b   Center for Molecular Biology and Biotechnology, Florida Atlantic University, Jupiter, Florida 33458, USA
› Author Affiliations
This work was supported by the NIH (R15GM116025) award.


Abstract

Nature remarkably employs posttranslational modifications of the 20 canonical α-amino acids to devise a far larger structural, conformational, and functional diversity found in non-proteinogenic amino acids (NPAAs), which ultimately translates into a plethora of complex biological functions. Synthetic chemists are continuously trying to reproduce and even extrapolate the repertoire of NPAA building blocks to build structural diversity into bioactive molecules and materials. The direct asymmetric functionalization of α-imino esters represents one of the most robust and attractive routes to NPAAs. This review summarizes the most prominent examples of bench-stable (ald)imine surrogates exploited for the synthesis of NPAAs, including our most recent results in the nucleophilic substitution of α-haloglycines and other α-halo­aminals. A synopsis of kinetic studies, reaction optimizations, and enantio­selective catalytic methods is also presented.

1 Introduction

2 Asymmetric Synthesis of Tertiary α-Substituted NPAAs

2.1 From N,O-Acetals (α-Hydroxy/Alkyloxy/Acetoxyglycines)

2.2 From α-Amido Sulfones

2.3 From α-Haloglycine Esters

2.4 From N,O-Bis(Boc) Hydroxyglycine

3 Asymmetric Synthesis of Acyclic Quaternary α,α-Disubstituted NPAAs

4 Concluding Remarks



Publication History

Received: 25 February 2021

Accepted after revision: 24 March 2021

Accepted Manuscript online:
24 March 2021

Article published online:
14 April 2021

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