Tetrazine-Ph-NHS ester

Tetrazine-Ph-NHS ester is a bifunctional PROTAC linker designed to combine a tetrazine moiety for bioorthogonal conjugation with an N-hydroxysuccinimide (NHS) ester handle for efficient coupling to primary amines. Its dual-reactivity enables modular assembly of targeted protein degradation constructs under mild conditions, supporting rapid synthesis of conjugates for structure–activity studies. The detailed structure and reactivity considerations are provided below.

Structure: The molecule contains a tetrazine-containing aromatic system linked to a phenyl group and an NHS ester functional group. It features an amide-forming acyl–oxygen leaving group within the NHS ester, along with conjugated heteroaromatic ring character that supports tetrazine reactivity. Overall polarity and reactivity are governed by the ester and heteroaromatic functionalities.

Reactivity: The NHS ester reacts with primary amines via acyl substitution to form stable amide bonds, typically using buffered aqueous or mixed solvent conditions that preserve amine nucleophilicity. Separately, the tetrazine moiety undergoes rapid inverse-electron-demand Diels–Alder chemistry with appropriate strained dienes (e.g., trans-cyclooctene derivatives) to enable selective conjugation. For PROTAC assembly, sequential coupling strategies and orthogonal timing are commonly used; catalysts are generally unnecessary, while solvent choice should minimize hydrolysis of the NHS ester and maintain tetrazine integrity.