Bis-BCN-PEG1-diamide

Bis-BCN-PEG1-diamide is a bifunctional PEG-based linker designed for constructing PROTACs through efficient conjugation to protein-binding ligands. Its flexible polyethylene glycol spacer supports productive ternary complex formation by improving linker solubility and conformational adaptability, while the two BCN (bicyclononyne) handles enable rapid, selective click-type coupling. The molecule is therefore well suited for assembling degrader architectures where controlled attachment chemistry and aqueous compatibility are critical. The detailed structural and reactivity considerations are provided below.

Structure: The linker contains a PEG segment providing hydrophilicity and conformational flexibility, flanked by two amide-linked reactive termini. BCN units present strained alkyne functionality suitable for cycloaddition, while the diamide connections help stabilize the linker backbone and maintain defined connectivity to partner ligands.

Reactivity: BCN-containing linkers are typically used in strain-promoted cycloaddition reactions with azide-bearing partners, proceeding without external catalysts. For PROTAC assembly, coupling is commonly performed in aqueous or mixed aqueous buffers compatible with biomolecular ligands, with mild temperature control to preserve ligand integrity. The reaction relies on the high reactivity of the strained BCN alkyne toward azides, enabling orthogonal, chemoselective conjugation under conditions that minimize side reactions.