DBCO-PEG5-acid

This DBCO-PEG5-acid linker is designed for efficient incorporation of a strained cyclooctyne handle into PROTAC architectures, enabling rapid bioorthogonal conjugation with azide-bearing ligands. Its PEG-based spacer improves solubility and reduces steric constraints, supporting productive ternary complex formation. The molecule is particularly useful for modular PROTAC assembly workflows, where orthogonal coupling steps can be performed under mild conditions. Detailed structural and reactivity considerations are provided below.

Structure: The linker contains a DBCO (dibenzocyclooctyne) strained alkyne for copper-free click reactivity, connected to a polyethylene glycol chain terminated by a carboxylic acid. It features ether linkages within the PEG segment, an alkyne-containing ring system, and an acid functional group for further derivatization.

Reactivity: The DBCO moiety reacts selectively with azides via strain-promoted azide–alkyne cycloaddition, typically without copper catalysis. For PROTAC construction, the carboxylic acid enables amide or ester formation using standard coupling chemistries under controlled pH, often with coupling reagents and base in compatible organic/aqueous mixtures. Solvent choice and concentration should preserve linker stability and maintain azide accessibility to drive efficient conjugation.