Carboxy-PEG3-mono-methyl ester
CAS No.: 1807505-26-5
Cat No.: BP-501273
Purity: ≥95%
4.5 
Carboxy-PEG3-mono-methyl ester is a short, water-compatible polyethylene glycol (PEG) linker bearing a terminal carboxylic acid for amide coupling and a monomethyl ester at the opposite end, enabling controlled attachment to PROTAC or related targeted degradation constructs. Structurally, it provides a three–ethylene glycol unit spacer that can increase solubility, reduce nonspecific hydrophobic contacts, and help position the recruited binder and the E3 ligase ligand at an appropriate distance and orientation. In PROTAC design, this type of bifunctional PEG linker is used to connect warhead and ligase-binding moieties through robust covalent chemistry, while the flexible PEG segment can modulate effective ternary complex formation and influence degradation potency and selectivity. Its compact length is particularly useful when excessive linker extension would impair geometry, making it valuable for systematic linker optimization in targeted protein degradation research.
Structure of 1807505-26-5
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Carboxy-PEG3-mono-methyl ester is a PEG-based PROTAC linker building block designed to introduce a flexible, hydrophilic spacer between targeting and recruiting ligands. Its ester functionality enables controlled conjugation strategies that support efficient synthesis of degraders while preserving conformational freedom and minimizing steric constraints. The linker is well suited for iterative PROTAC assembly, and the detailed structural and reactivity considerations are provided below.
Structure: The molecule contains a short polyethylene glycol chain terminated by a carboxylate-derived group and a methyl ester, providing a flexible, ether-rich backbone. It features ether linkages within the PEG segment and an ester carbonyl, which together confer polarity, hydrogen-bonding capacity, and hydrolytic susceptibility.
Reactivity: The carboxylate-derived ester can participate in standard PROTAC conjugation workflows such as ester activation followed by nucleophilic acyl substitution to form amide or related linkages with ligand-bearing nucleophiles. Typical approaches rely on coupling reagents and bases under mild organic solvent conditions to preserve PEG integrity. Mechanistically, acyl activation increases electrophilicity, enabling controlled bond formation while maintaining the linker’s spacer function.
* 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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