Mild Bioconjugation Through the Oxidative Coupling of ortho‐Aminophenols and Anilines with Ferricyanide

Abstract

Using a small-molecule-based screen, ferricyanide was identified as a mild and efficient oxidant for the coupling of anilines and o-aminophenols on protein substrates. This reaction is compatible with thiols and 1,2-diols, allowing its use in the creation of complex bioconjugates for use in biotechnology and materials applications.

Controlled levels of protein modification through a chromatography-mediated bioconjugation

“…15,16 As an example, a sample of singly tagged RNAse A was exposed to sodium dithionite to unmask the aniline functionality of the azo handle (Fig. 2i).…”

Direct detection of nitrotyrosine-containing proteins using an aniline-based oxidative coupling strategy

“…In our lab, aminophenols have been central to a series of chemoselective oxidative coupling (OC) strategies, 18,19 which have involved the facile addition of anilines to iminoquinone intermediates resulting from oxidation with periodate 18,20 or ferricyanide, Figure 1, step 2. 21 A closely related strategy has been reported for Y-NO 2 detection by the Schöneich group, 15,16 in which benzylamine derivatives are coupled to the same intermediate. Their strategy leads to the formation of a new fluorophore and the simultaneous attachment of a diol handle for use in boron-based affinity chromatography.…”

“…Based on our experience with the OC strategy for the preparation of complex bioconjugates, 21 we hypothesized that suitably-functionalized anilines would offer higher coupling yields at lower pH values, and the formation of single products rather than mixtures. The reaction exhibits very high rates and chemoselectivities at pH 6.0 to 6.5, and is compatible with glycoproteins, 22 nucleic acids, 20 and complex molecular structures.…”

An Oxidative Bioconjugation Strategy Targeted to a Genetically Encoded 5‐Hydroxytryptophan

“…Identification of electron-rich aromatic groups that could be chemoselectively functionalized under mild oxidative conditions, and the ability to site-specifically incorporate them into target proteins can create new approaches for site-selective protein labeling. [4] Here we show that the 5-hydroxytryptophan (5HTP) residue, which has been recently genetically encoded in both E. coli and eukaryotes, [5] can be selectively and efficiently labeled with a variety of aromatic amines under relatively mild oxidative conditions.…”

“…Aromatic amines have been used as coupling partners with much success in analogous oxidative coupling reactions targeted to electron-rich functionalities such as aminophenols. [4a-c] To trigger similar oxidative coupling reaction on proteins, relatively mild oxidants such as ferricyanide and periodate have been employed. [4] We noted that the treatment of free 5HTP with potassium ferricyanide led to its rapid conversion to a complex product mixture (Figure S1), indicating the potential suitability of this reagent to trigger its oxidative modification.…”