An Orthogonally Functionalizable Tetrazine Building Block for Dual-Conjugated Bioorthogonal Probes

The development of multifunctional bioorthogonal tools is essential for expanding their utility in biomedical research. Here, we report a gram-scale accessible building block, 3-(mesyloxyethyl)-6-(diethylphosphonomethyl)-tetrazine, featuring two orthogonal reactive handles. This scaffold enables the modular construction of a series of dual-conjugated tetrazine probes with versatile functionalities. Remarkably, the dual-conjugated architecture was found to induce bathochromic emission in the resulting bioorthogonal adducts, thereby facilitating new fluorophores <i>in situ</i> formation and offering a promising platform for the design of theranostic agents.