Tos-PEG4-O-CH2COOH
CAS No.: 2028284-73-1
Cat No.: BP-500818
Purity: ≥95%
4.5 
Tos-PEG4-O-CH2COOH is a tosyl-terminated polyethylene glycol linker featuring a four–ethylene glycol unit chain and an ether linkage to a terminal glycolic acid (O–CH2–COOH) group. The tosyl group provides a robust leaving group for nucleophilic substitution, enabling efficient conjugation to amine- or thiol-containing ligands under standard PROTAC linker-assembly conditions, while the carboxylic acid end offers a convenient handle for further functionalization (e.g., amide coupling) or for tuning solubility and polarity of the final degrader. In PROTAC design, such PEG linkers are widely used to spatially separate the target-binding and E3-ligase-binding moieties, reducing steric interference and helping maintain productive ternary complex formation. This product is therefore valuable for constructing modular, water-compatible PROTACs and related targeted protein degradation probes, where controlled linker length and terminal reactivity are critical for optimizing synthesis yield and biological performance.
Structure of 2028284-73-1
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Tos-PEG4-O-CH2COOH is a PEG-based linker designed for constructing PROTACs and related targeted protein degradation conjugates. Its ether-rich polyethylene glycol segment provides conformational flexibility and improved solubility, while the terminal carboxylic acid enables reliable attachment to ligands or handles for subsequent coupling steps. The following sections describe the linker’s structure and practical reactivity considerations for PROTAC synthesis.
Structure: The molecule contains a PEG chain featuring repeating ether linkages and an aryl sulfonate (tosyl) group, terminating in a hydroxymethyl carboxylic acid functionality. It is stabilized by ether and sulfonate-derived bonding, with a polar, hydrogen-bonding-capable end group that supports aqueous compatibility.
Reactivity: The terminal carboxylic acid can be activated for amide or ester bond formation using standard coupling chemistries such as carbodiimide-mediated activation with appropriate additives, or via acid chloride intermediates under controlled conditions. The tosyl group can serve as a leaving group in substitution-based transformations, enabling formation of linker-ligand connections. Typical PROTAC assembly employs polar organic solvents and base/acid conditions compatible with ligand stability.
* 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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