tert-Butyl 11-azido-3,6,9-trioxaundecanoate

This tert-Butyl 11-azido-3,6,9-trioxaundecanoate linker is designed for modular PROTAC assembly, providing a stable, protected handle for subsequent functionalization and a terminal azide for bioorthogonal conjugation. Its ether-rich, flexible scaffold supports productive spatial orientation between the E3 ligase ligand and target-binding moieties, while the azide enables efficient “click” coupling strategies. The following sections describe its structural features and practical reactivity considerations in PROTAC workflows.

Structure: The linker contains a tert-butyl ester protecting group and a terminal azide, connected through an ether-rich, poly(ethylene glycol)-like chain. It features ester and ether linkages, along with an azide functional group suitable for cycloaddition chemistry. Overall, it is conformationally flexible and polarity-enhancing, supporting solubility in common organic solvents.

Reactivity: The azide group is well suited for copper(I)-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkene variants, enabling rapid conjugation to appropriately functionalized PROTAC fragments. Ester functionality can be retained during coupling or selectively deprotected under standard acid conditions to reveal carboxylate for amide coupling. Typical PROTAC synthesis uses inert atmosphere, dry polar solvents, and copper-free conditions when sensitive ligands are present.