DBCO-NHCO-PEG13-acid

This DBCO-functionalized PEG linker is designed for efficient, modular assembly of PROTACs via strain-promoted azide–alkyne cycloaddition (SPAAC). Its PEG-based spacer improves solubility and provides conformational flexibility between the targeting ligand and the E3 ligase moiety, which can help preserve productive ternary complex formation. The DBCO handle enables bioorthogonal conjugation under mild conditions, making it suitable for streamlined linker–ligand coupling workflows. Detailed structural and reactivity considerations are provided below.

Structure: The linker combines a DBCO cyclooctyne core with an amide linkage and a PEG spacer terminating in a carboxylic acid. It contains heteroatoms (oxygen and nitrogen) that support hydrogen bonding, along with an alkyne-based strained ring for rapid cycloaddition. The PEG segment imparts hydrophilicity and flexibility.

Reactivity: DBCO reacts selectively with azides through SPAAC, proceeding without copper catalysis and typically under aqueous or mixed aqueous conditions at moderate temperatures. The cycloaddition forms a stable triazole linkage, enabling conjugation of azide-functionalized ligands or PROTAC components. For carboxylic acid utilization, standard amide-coupling strategies (e.g., carbodiimide-mediated coupling with an appropriate base) can be used to attach the linker to amine-bearing partners.