Fast Bioorthogonal Ligation of 2-Aminobenzohydrazides and (2-Acetylphenyl)boronic Acids Providing Stable and Fluorescent Conjugates

Bioorthogonal chemistry has become an extremely powerful tool in many fields, and a variety of bioorthogonal reactions have been developed. However, the ideal bioorthogonal reactions are very limited because of the demanding requirements of bioorthogonal chemistry. Here, we report a novel and robust bioorthogonal ligation of readily available 2-aminobenzohydrazides and (2-acetylphenyl)boronic acids, in which combined common functional groups such as amino, acylhydrazino, acetyl, and boric acid were used as the reporter groups. The reactions proceeded well in organic solvents, water, cell growth medium, or cell lysate. This high reactivity was applied in protein modification at low concentrations under physiological conditions. The bioorthogonal ligation exhibits some advantages, including tolerance of a wide range of functional groups, fast rates (up to k2 = 24.7 M–1 s–1), almost quantitative yields, water being the only byproduct, the high stability of conjugates under physiological conditions, and the obtained conjugates showing fluorescence, and represents a new approach for the fluorescent labeling of biomolecules.