Optimization of the azobenzene scaffold for reductive cleavage by dithionite; development of an azobenzene cleavable linker for proteomic applications
In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo-arene group. Our stepwise investigation allowed identification of a highly reactive azo-arene structure 25 bearing a carboxylic acid, at the ortho position of the electron-poor arene and an ortho-Oalkyl-resorcinol as the electron-rich arene. Based on this 2(2′-alkoxy-4′-hydroxyphenylazo) benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo-arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo-arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media.
MECHANISM OF THE REACTION OF ACETYL HALIDES WITH AROMATIC AMINES IN THE PRESENCE OF N-SUBSTITUTED IMIDAZOLES
The effect of the structure of aromatic amines and the nature of the leaving group in N-acetylimidazolium chlorides in reactions leading to the formation of amides in methylene chloride at 25 deg C was investigated.The possibility of stabilization of the transition state of the bimolecular reaction on account of general-base assistance on the part of the anion of the salt was demonstrated by analysis of the sensitivity of the bimolecular reaction of the acylimidazolium salt with aromatic amines to the nature of attacking and leaving groups.At the same time the mechanism of the trimolecular reaction of the salt with the arylamine does not fit into the scheme of the general-base catalysis by the anion and is interpreted by the inclusion of aggregates of N-acetylimidazolium halides in the transition state of trimolecular reaction.
Lapshin, S. A.,Dadali, V. A.,Litvinenko, L. M.,Simanenko, Yu. S.
p. 1730 - 1735
(2007/10/02)
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