Click-to-Release Reactions for Tertiary Amines and Pyridines

Click-to-release reactions, transformations that liberate molecules of interest under physiological conditions, are gaining traction as powerful means to control biological processes and enable spatiotemporal drug delivery. A major limitation of current click-to-release strategies remains their narrow scope of releasable functional groups, leaving many classes of bioactive molecules incompatible with such approaches. This study provides the first examples of click-to-release reactions for tertiary amines and pyridines. Two orthogonal strategies were developed based on bioorthogonal reactions between isonitriles and tetrazines. Isocyanopropyl (ICPr) groups were used to cage tertiary amines and pyridines, enabling their release upon reaction with tetrazines under mild conditions. Similarly, tetrazylmethyl (TzMe) groups masked these functionalities for liberation by isonitriles. Interestingly, while the removal of TzMe groups with primary isonitriles did not occur as originally intended, tertiary isonitriles mediated efficient release. Experimental and computational studies revealed an unexpected pathway distinct from the previously reported mechanisms for TzMe deprotection. The masking groups could be successfully applied to a range of bioactive molecules, and the resulting precursors exhibited good stability in the buffer. Preliminary studies in zebrafish embryos established the bioorthogonality of the reactions. Together, this work significantly expands the repertoire of releasable groups for click-to-release chemistry and opens new opportunities for applications in chemical biology and targeted drug delivery.