RESUMO
An unprecedented intramolecular [4 + 2] tetrazine-olefin cycloaddition with α,ß-unsaturated substrates was discovered. The reaction produces unique coumarin-dihydropyridazine heterocycles that exhibited strong fluorescence with large Stokes shifts and excellent photo- and pH-stability. This property can be used for reaction analysis. The rate of cycloaddition was found to be solvent dependent and was determined using experimental data with a kinetic modeling software (COPASI) as well as DFT calculations (k 1 = 0.64 ± 0.019 s-1 and 4.1 s-1, respectively). The effects of steric and electronic properties of both the tetrazine and α,ß-unsaturated carbonyl on the reaction were studied and followed the known trends characteristic of the intermolecular reaction. Based on these results, we developed a "release-then-click" strategy for the ROS triggered release of methylselenenic acid (MeSeOH) and a fluorescent tracer. This strategy was demonstrated in HeLa cells via fluorescence imaging.
RESUMO
In this work we studied the reactions of benzothiazole sulfones and sulfoxides toward reactive sulfur species. The reaction of thiols with benzothiazole sulfones produces sulfinic acids (RSO2H), which can further react with sulfane sulfurs to form thiosulfonic acids (RSO2SH). This was used to design fluorescent sensors for hydrogen polysulfides. The reaction of thiols with benzothiazole sulfoxides produces sulfenic acids (RSOH), which can undergo fast intramolecular cyclization and be used to design thiol-triggered fluorescent sensors.
