Tos-PEG21-Tos
Cat No.: BP-501771
4.5 
Tos-PEG21-Tos is a bifunctional polyethylene glycol (PEG) linker bearing two tosyl (tosylate) termini, providing a flexible, water-compatible chain length with a defined end-group chemistry for PROTAC assembly. Structurally, the central PEG segment acts as a hydrophilic spacer that can reduce steric interference between the two ligands while maintaining sufficient conformational freedom to promote productive ternary complex formation. The terminal tosylates serve as activated leaving groups for nucleophilic substitution, enabling efficient conjugation to complementary functional handles (e.g., amines or thiols) on E3 ligase recruiters and target-binding moieties. In targeted protein degradation research, such PEG-based linkers are widely used to tune linker length, polarity, and effective reach, thereby optimizing degradation potency and selectivity while improving solubility and handling of assembled PROTACs. This product is therefore valuable for systematic linker optimization and for constructing reproducible, end-functionalized PROTAC intermediates for downstream synthesis and evaluation.
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* For research and manufacturing use only. Not for human or clinical use.
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- Comprehensive PROTAC Platform
- Scientific Expertise & Technical Support
- Custom Synthesis & Design Service
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Popular Publications Citing BOC Sciences Products
Tos-PEG21-Tos is a heterobifunctional PEG-based linker engineered for PROTAC assembly, offering a flexible, water-compatible spacer between two reactive termini. Its ether-rich poly(ethylene glycol) scaffold can enhance solubility and reduce steric bias, supporting efficient formation of productive ternary complexes. The two tosyl-activated ends enable straightforward conjugation to appropriate nucleophiles, and the linker is described in detail below for structure and reactivity considerations.
Structure: The linker comprises a poly(ethylene glycol) chain terminated by tosylate groups, featuring ether linkages along the PEG backbone and sulfonate ester functionality at both ends. The aromatic tosyl fragments provide stable leaving groups, while the extended, flexible chain imparts high hydrophilicity and conformational mobility.
Reactivity: Tosylate termini are well suited for nucleophilic substitution reactions, where suitable nucleophiles (commonly amines or thiols) displace the tosylate under base-promoted conditions. Linker conjugation is typically performed in polar aprotic or mixed solvent systems compatible with both nucleophile and substrate, with temperature and time optimized to preserve functional groups. The overall mechanism follows bimolecular substitution, and no special catalysts are generally required beyond appropriate base selection.
* Our calculator is based on the following equation:
Concentration (start) x Volume (start) = Concentration (final) x Volume (final)
It is commonly abbreviated as: C1V1 = C2V2
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