m-PEG5-Tos

m-PEG5-Tos is a polyethylene glycol-based tosylate linker designed for efficient installation of PEG spacers in PROTAC architectures. Its ether-rich, flexible scaffold can improve solubility and modulate the effective distance between ligand-binding elements, supporting controlled formation of ternary complexes. The terminal tosylate provides a robust leaving group for linker conjugation, enabling streamlined synthesis of targeted protein degraders.

Structure: The linker consists of a PEG chain terminated by a tosylate (tosylate ester) group. It contains ether linkages along the PEG backbone and an aromatic sulfonate ester at the terminus. This combination yields a flexible, polar, and generally water-compatible scaffold suitable for bioconjugation workflows.

Reactivity: The terminal tosylate is primed for nucleophilic substitution, where an appropriate nucleophile (commonly an amine or phenoxide/thiolate, depending on the partner) displaces the tosylate to form a new C–N, C–O, or C–S bond. Typical conditions employ polar aprotic solvents with base to generate the nucleophile, often under mild, anhydrous handling to minimize side reactions.