In Situ Synthesis of Alkenyl Tetrazines for Highly Fluorogenic Bioorthogonal Live‐Cell Imaging Probes

Abstract

In spite of the wide application potential of 1,2,4,5tetrazines, particularly in live-cell and in vivo imaging, a major limitation has been the lack of practical synthetic methods. Here we report the in situ synthesis of (E)-3-substituted 6alkenyl-1,2,4,5-tetrazine derivatives through an elimination-Heck cascade reaction. By using this strategy, we provide 24 examples of p-conjugated tetrazine derivatives that can be conveniently prepared from tetrazine building blocks and related halides. These include tetrazine analogs of biological small molecules, highly conjugated buta-1,3-diene-substituted tetrazines, and a diverse array of fluorescent probes suitable for live-cell imaging. These highly conjugated probes show very strong fluorescence turn-on (up to 400-fold) when reacted with dienophiles such as cyclopropenes and trans-cyclooctenes, and we demonstrate their application for live-cell imaging. This work provides an efficient and practical synthetic methodology for tetrazine derivatives and will facilitate the application of conjugated tetrazines, particularly as fluorogenic probes for live-cell imaging.

In situ click chemistry generation of cyclooxygenase-2 inhibitors

“…Here, we deviated from conventional drug discovery approaches involving the laborious synthesis and screening of a range of compounds, and envisioned to explore the utility of in situ click chemistry for the discovery of specific and high-affinity COX-2 inhibitors. Click chemistry 32 , 33 , including 1,3-dipolar cycloaddition between alkyne and azide (Huisgen cycloaddition), have attracted much attention because of their remarkable efficiency, simplicity, and its ability to be employed for the synthesis of a wide range of compounds such as molecular imaging agents 34 , 35 and drugs 36 , protein modification 37 , 38 , DNA and RNA targeting 39 , 40 , and glycan imaging 41 , 42 . Considering its versatility, click chemistry has found numerous synthesis applications not only performed in traditional reaction vessels, but also in living systems.…”

Donor–Acceptor 1,2,4,5-Tetrazines Prepared by the Buchwald–Hartwig Cross-Coupling Reaction and Their Photoluminescence Turn-On Property by Inverse Electron Demand Diels–Alder Reaction

“…1,2 Applications spanning biological imaging and detection, cancer targeting, drug delivery and biomaterials science have been recently demonstrated. [3][4][5][6][7][8][9][10][11][12][13] Moreover, for the past several decades electron-deficient 1,2,4,5-tetrazine molecules have been found particularly useful in various fields 14 such as organic electronics (e.g., OPVs, OFETs), [15][16][17] energetic materials, 18,19 coordination chemistry, [20][21][22] electrofluorochromism 23 and total synthesis of natural products. 24,25 The most widely used method for the synthesis of 1,2,4,5tetrazines is a two-step procedure starting from the addition of hydrazine to nitrile precursors, followed by the oxidation of the resulting 1,2-dihydrotetrazine.…”

Synthesis, Structure, and Molecular Recognition of S6‐ and (SO2)6‐Corona[6](het)arenes: Control of Macrocyclic Conformation and Properties by the Oxidation State of the Bridging Heteroatoms

“…Polyfunctionality and easy availability rendered the resulting S 6 -corona [3]arene [3]tetrazines 3 and 6 invaluable molecular platformsf or the constructiono fo ther sophisticated macrocycles. As important N-heterocyclic compounds, 1,2,4,5-tetrazine and its derivatives not only have wide applicationsint he preparation of coordination polymers [30] and in labeling and imaging biological macromolecules and living systems, [31] they are also frequently used in organic synthesis because they are able to undergo cycloaddition reactions with many electron-rich dienophiles to form new aromatic rings. [32] On the other hand, sulfide linkages in S 6 -corona [6](het)arenes would provide au nique opportunity to diversify the macrocyclic skeletons because oxidationo fas ulfide would lead to the formation of as ulfoxide and as ulfone.…”