Tos-PEG4-acid
CAS No.: 1453117-42-4
Cat No.: BP-501397
Purity: ≥95%
4.5 
Tos-PEG4-acid is a PEG-based linker reagent featuring a tosyl (tosylate) functional group at one terminus and a carboxylic acid at the other, providing a flexible, water-soluble chain of defined length suitable for bioconjugation. In PROTAC and targeted protein degradation designs, such linkers are commonly used to spatially separate a ligand that recruits an E3 ligase from a ligand that binds the target protein, thereby tuning effective intramolecular proximity and reducing steric interference. The tosylate handle can serve as an electrophilic activation site for coupling to nucleophilic groups on partner molecules, while the terminal acid enables further derivatization (e.g., amide formation) to generate stable conjugates. Its PEG architecture can improve aqueous compatibility and often helps maintain solubility of multicomponent degraders, facilitating systematic structure–activity studies and optimization of degradation potency and selectivity.
Structure of 1453117-42-4
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Tos-PEG4-acid is a PEG-based PROTAC linker designed to provide a hydrophilic, flexible spacer between a target-binding ligand and an E3 ligase recruiting element. Its ether-rich backbone supports favorable solubility and conformational freedom, which can help maintain productive ternary complex formation. The acidic terminus enables practical functionalization for PROTAC assembly. The structure and reactivity considerations are described in detail below.
Structure: Tos-PEG4-acid comprises a PEG chain bearing a terminal tosylate leaving group and a carboxylic acid, with multiple ether linkages that confer flexibility and strong hydrogen-bonding capacity. The molecule contains an alkyl tosylate and a terminal carboxylic acid, providing distinct orthogonal handles for substitution and acyl-coupling steps.
Reactivity: The terminal carboxylic acid can be activated for amide or ester bond formation, typically using standard coupling chemistries that proceed via an acyl-activation intermediate. The tosylate is a leaving group suited to SN2 substitution with suitable nucleophiles rather than a protecting group that must be removed by deprotection. For PROTAC synthesis, compatible polar solvents and mild base conditions are commonly employed to preserve labile ligand functionalities and minimize side reactions.
* 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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