Design and synthesis of tetrazine bioorthogonal fluorogenic probes / 药学学报

Bioorthogonal fluorogenic probes are becoming an ideal tool for live-cell fluorescence imaging. With the tetrazine bioorthogonal fluorogenic probe that displays fluorescence enhancement, the tetrazine plays the dual-role of a bioorthogonal reaction unit and the fluorescence quenching unit. The "off" and "on" states of the fluorescence probe are mainly controlled through inverse electron demand Diels-Alder (IEDDA) bioorthogonal reaction. We designed a series of turn-on tetrazine fluorescent probes with Donor-π-Acceptor (D-π-A) structure to achieve a high signal-to-noise ratio and specificity of fluorescence imaging. This series of probes reacted with the dienophile bicyclononyne, and then generated pyridazine structure in-situ that acted as an electron acceptor, resulting in a new D-π-A effect of fluorescent dyes, turning on the intramolecular charge transfer (ICT) effect. By adjusting the electron-donating groups and the degree of conjugation, tunable fluorescence spectra between 400-647 nm with fluorescence turn-on enhanced up to 500-fold have been achieved. This research lays the foundation for the further optimization of tetrazine bioorthogonal fluorescent probes and their applications in molecular imaging and biomedical fields.

Reaction of phenylhydrazo ethylacetoacetate with cyano acetyl hydrazine: Novel synthesis of pyridazine and pyrazole derivatives and their anti-tumor evaluations.

The reaction of phenylhydrazoethyl acetoacetate (1) with cyanoacetyl hydrazine (2) in an oil bath in the presence of ammonium acetate gave the pyridazine derivative 4. However, carrying the same reaction but in ethanolic/Et3N gave the pyrazole derivative 5. Compounds 4 and 5 were used in a series of heterocyclization reactions to afford products that showed anti-tumor activities towards three cell lines namely, breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and CNS cancer (SF- 268).