-Terminal Cysteine Bioconjugation with (2-Cyanamidophenyl)boronic Acids Enables the Direct Formation of Benzodiazaborines on Peptides.

Benzodiazaborines (BDABs) have emerged as a valuable tool to produce stable and functional bioconjugates via a click-type transformation. However, the current available methods to install them on peptides lack bioorthogonality, limiting their applications. Here, we report a strategy to install BDABs directly on peptide chains using (2-cyanamidophenyl)boronic acids (2CyPBAs).

Interactive Bioconjugation at N-Terminal Cysteines by Using O-Salicylaldehyde Esters towards Dual Site-Selective Functionalization.

N-terminal Cys modification has been intensively studied to produce homogeneous bioconjugates essentially through two modes of reaction: reversible modification with the equilibrium shifted towards the formation of the desired conjugate or stable and irreversible conjugates. Herein, we report a new method of N-terminal cysteine modification using O-salicylaldehyde esters (OSAEs) through fast conjugation and irreversible deconjugation. These reagents can rapidly react with N-terminal Cys at low-micromolar concentration to form thiazolidines with subsequent hydrolysis of the ester moiety to the phenolic derivative.