Glycine Imine—The Elusive α‐Imino Acid Intermediate in the Reductive Amination of Glyoxylic Acid

Abstract

Simple unhindered aldimines tend to hydrolyze or oligomerize and are therefore spectroscopically not well characterized. Herein we report the formation and spectroscopic characterization of the simplest imino acid, namely glycine imine, by cryogenic matrix isolation IR and UV/Vis spectroscopy. Glycine imine forms after UV irradiation of 2‐azidoacetic acid by N2 extrusion in anti‐(E,E)‐ and anti‐(Z,Z)‐conformation that can be photochemically interconverted. In matrix isolation pyrolysis experiments with 2‐azidoacetic acid, glycine imine cannot be trapped as it further decarboxylates to aminomethylene. In aqueous solution glycine imine is hydrolyzed to hydroxy glycine and hydrated glyoxylic acid. At higher concentrations or in the presence of FeIISO4 as a reducing agent glycine imine undergoes self‐reduction by oxidative decarboxylation chemistry. Glycine imine may be seen as one of the key reaction intermediates connecting prebiotic amino acid and sugar formation chemistry.

Enantiodetermining processes in the synthesis of alanine, serine, and isovaline

“…Numerous subsequent studies have proposed diverse routes to Gly on interstellar ices/grains. [7][8][9][10][11][12][13][14][15][16][17][18] A variety of gas-phase synthesis pathways of Gly have also been explored, including reactions involving acetic acid, carboxylic acids, carboxyl radical, amino radical, methylene radical, methylidyne radical, and carbon monoxide. [19][20][21][22][23][24][25] In contrast to the extensive research on Gly, only a few studies have been conducted on the interstellar formation of other a-amino acids e.g.…”

Spectroscopic identification of interstellar relevant 2-iminoacetaldehyde

“…We demonstrated recently the selective formation of reactive imine intermediates in cryogenic matrix isolation studies. 11 1,2-diiminoethane, a key intermediate in the synthesis of imidazole, was prepared in a photolysis experiment of 1,2-diazidoethane in solid argon at 3 K and characterized by infrared (IR) and UV/Vis spectroscopy. 11 a In a similar fashion we prepared and spectroscopically characterized glycine imine ( 5 ), the simplest α-imino acid as a critical precursor for the synthesis of glycine and glyoxylic acid.…”