Ethynyl-Tetrazines: A Clickable Reagent for Universal Access to Rapid and Stable Bioorthogonal Probes

Abstract

Abstract Despite the tetrazine bioorthogonal reaction holding immense potential in biomedical research and drug discovery, its in vivo performance has been strongly challenged by the inverse correlation between the physiological stability and reactivity of tetrazines. Moreover, the preparation of tetrazine is typically complex and requires restricted reagents. To overcome these challenges, we describe a scalable approach to synthesize a range of shelf-stable ethynyl-tetrazines. By using ethynyl-tetrazine as a clickable precursor, we can modularly access a new type of highly reactive functionalized triazolyl-tetrazines with improved stability for use in biomedical applications. We demonstrate the efficacy of this approach by efficiently constructing 18F-labeled tetrazine derivatives with radiochemical yields of up to 84%, and tunable biodistribution patterns for PET (positron emission tomography) imaging. This approach will significantly facilitate the application of tetrazine bioorthogonal chemistry in biomedical research, theranostics, and materials science.