Gly-PEG3-endo-BCN

Gly-PEG3-endo-BCN is a bifunctional PEG-based linker designed for efficient conjugation in targeted protein degradation workflows. Its endo-bicyclononyne (endo-BCN) handle enables rapid bioorthogonal ligation with azide-bearing partners, while the glycine-PEG segment provides solubility and conformational flexibility that can improve PROTAC assembly and performance. The detailed structural and reactivity characteristics of this linker are described below.

Structure: The molecule comprises a glycine-derived segment connected to a short polyethylene glycol chain, terminating in an endo-bicyclononyne functionality. It contains ether linkages within the PEG backbone and amide connectivity associated with the glycine unit. The endo-BCN moiety is a strained alkyne designed for cycloaddition.

Reactivity: The endo-BCN group is suited for strain-promoted azide–alkyne cycloaddition with azide-functional ligands under mild, catalyst-free conditions. PROTAC synthesis typically proceeds by mixing azide-bearing targeting or warhead components with the linker in compatible aqueous or mixed solvent systems to maintain solubility. Reaction progress can be monitored by analytical methods such as LC-MS or HPLC, leveraging the high chemoselectivity of the SPAAC mechanism.