DBCO-PEG4-DBCO

This bifunctional DBCO-PEG linker is designed for efficient, catalyst-free conjugation in PROTAC assembly workflows that rely on copper-free click chemistry. Its two DBCO termini enable orthogonal attachment to complementary azide-bearing ligands, while the PEG spacer improves solubility and reduces steric constraints during target engagement. The linker’s modular architecture supports reproducible synthesis of PROTAC constructs, and the detailed structure and reactivity considerations are provided below.

Structure: The molecule comprises two cyclooctyne (DBCO) moieties connected through a polyethylene glycol (PEG) chain, providing flexible, ether-rich spacing. It contains strained alkene functionality characteristic of DBCO, plus ether linkages that impart hydrophilicity and conformational mobility. Overall, it behaves as a bifunctional click handle for conjugation.

Reactivity: DBCO groups undergo strain-promoted azide–alkyne cycloaddition with azides under copper-free conditions. For PROTAC linker construction, ligands bearing terminal azides are reacted with this DBCO-PEG-DBCO to form stable triazole linkages via a concerted cycloaddition mechanism. Typical conditions use polar organic or mixed aqueous solvents compatible with biomolecule stability, and reactions are generally performed at mild temperature with appropriate stoichiometry to favor complete bis-conjugation.