DBCO-PEG4-acid

This DBCO-PEG4-acid linker is designed for modular PROTAC assembly by providing a strained cyclooctyne handle (DBCO) for bioorthogonal conjugation and a PEG spacer that improves solubility and presentation of attached ligands. Its carboxylic acid functionality enables reliable coupling to targeting moieties, supporting efficient construction of degraders through orthogonal chemistry. Detailed structural and reactivity considerations are provided below to guide experimental workflows.

Structure: The linker combines a DBCO (dibenzocyclooctyne) strained-alkyne core with an oligo(ethylene glycol) spacer and a terminal carboxylic acid. It contains a rigid cyclooctyne ring, ether linkages in the PEG segment, and a carboxylate-forming functional group, supporting aqueous compatibility and stable covalent attachment strategies.

Reactivity: DBCO reacts selectively with azide-functional partners via strain-promoted azide–alkyne cycloaddition, typically under mild, catalyst-free conditions. For PROTAC synthesis, the carboxylic acid is commonly activated for amide or ester formation with amine- or alcohol-bearing ligands, followed by DBCO–azide “click” conjugation to assemble the final construct. Reactions are generally performed in polar organic or mixed aqueous solvents, using standard coupling activators and base systems compatible with azide stability.