Engineering Alloxazines by Boron Coordination and Click Chemistry toward Small-molecule Fluorescent Probes

Selective and strategic modification of redox cofactors offers significant advantages for the design of molecular probes, including high compatibility and affinity. This is particularly relevant in the case of redox cofactors with innate fluorescence properties, such as flavins, and synthetic strategies toward their functionalized analogues are of high interest to modulate properties. However, the synthetic elaboration of flavins and their alloxazine isomers still suffers from limitations. We report easy access to bioinspired fluorescent alloxazines with a boron difluorocatecholate moiety and explore the impact of core aromatic substitution on their photophysical properties. Further chemical elaboration through a CuAAC (copper-catalyzed azide-alkyne cycloaddition) click chemistry strategy opens the way to easy derivatization and further addressing.