5-((8-Hydroxyquinolin-5-yl)diazenyl)-3-methyl-1H-pyrazole-4-carboxylic Acid

A new azo compound was prepared via the azo coupling reaction between 4-(ethoxycarbonyl)-3-methyl-1H-pyrazole-5-diazonium chloride and 8-hydroxyquinoline (oxine). The ester functional group of the obtained compound was hydrolyzed and thus a new chemical structure with a carboxylic functional group resulted. The structures of the new compounds were fully characterized by: UV–Vis, FT-IR, 1D and 2D NMR spectroscopy, and HRMS spectrometry.

An Azo Coupling-Based Chemoproteomic Approach to Systematically Profile the Tyrosine Reactivity in the Human Proteome

<p>The tyrosine residue of proteins participates in a wide range of activities including enzymatic catalysis, protein-protein interaction, and protein-ligand binding. However, the functional annotation of the tyrosine residues on a large scale is still very challenging. Here, we report a novel method integrating azo coupling, bioorthogonal chemistry, and multiplexed proteomics to globally investigate the tyrosine reactivity in the human proteome. Based on the azo-coupling reaction between aryl diazonium salt and the tyrosine residue, the two different probes were evaluated, and the probe with the best performance was employed to specifically target the tyrosine residues. After the reaction, tagged tyrosine containing peptides were selectively enriched using bioorthogonal chemistry, and a small tag on the peptides from the cleavage perfectly fits for site-specific analysis by MS. Coupling with multiplexed proteomics, we quantified over 5,000 tyrosine sites in MCF7 cells and these quantified sites displayed a wide range of reactivity. The tyrosine residues with high reactivity were found on functionally and structurally diverse proteins, including those with the catalytic activity and binding property. This method can be extensively applied to advance our understanding of protein functions and facilitate the development of covalent drugs to regulate protein activity.</p>

An Azo Coupling-Based Chemoproteomic Approach to Systematically Profile the Tyrosine Reactivity in the Human Proteome

<p>The tyrosine residue of proteins participates in a wide range of activities including enzymatic catalysis, protein-protein interaction, and protein-ligand binding. However, the functional annotation of the tyrosine residues on a large scale is still very challenging. Here, we report a novel method integrating azo coupling, bioorthogonal chemistry, and multiplexed proteomics to globally investigate the tyrosine reactivity in the human proteome. Based on the azo-coupling reaction between aryl diazonium salt and the tyrosine residue, the two different probes were evaluated, and the probe with the best performance was employed to specifically target the tyrosine residues. After the reaction, tagged tyrosine containing peptides were selectively enriched using bioorthogonal chemistry, and a small tag on the peptides from the cleavage perfectly fits for site-specific analysis by MS. Coupling with multiplexed proteomics, we quantified over 5,000 tyrosine sites in MCF7 cells and these quantified sites displayed a wide range of reactivity. The tyrosine residues with high reactivity were found on functionally and structurally diverse proteins, including those with the catalytic activity and binding property. This method can be extensively applied to advance our understanding of protein functions and facilitate the development of covalent drugs to regulate protein activity.</p>

Crystal structure of 2-[(E)-2-(4-bromophenyl)diazen-1-yl]-4,5-bis(4-methoxyphenyl)-1H-imidazole: the first example of a structurally characterized triarylazoimidazole

The title compound, C23H19BrN4O2, is a product of an azo coupling reaction between 3,4-bis(4-methoxyphenyl)imidazole and 4-bromophenyldiazonium tetrafluoroborate. Its crystal structure was determined using data collected at 120 K. The molecule adopts a trans configuration with respect to the N=N double bond. The imidazole and aryl rings attached to the azo linkage are coplanar within 12.73 (14)°, which indicates significant electron delocalization within the molecule. In the crystal, the molecules form centrosymmetric dimers via pairs of N—H...O hydrogen bonds.