Fmoc-NH-PEG25-CH2CH2COOH
Cat No.: BP-502091
4.5 
Fmoc-NH-PEG25-CH2CH2COOH is a heterobifunctional, Fmoc-protected PEG-based linker bearing a terminal carboxylic acid and an ethylene spacer (–CH2CH2–) that terminates in a free acid for subsequent coupling. Structurally, it combines an Fmoc group for solid-phase or stepwise synthetic handling with a long, flexible polyethylene glycol chain that provides hydrophilicity, conformational freedom, and improved solubility for conjugation workflows. In PROTAC and targeted protein degradation designs, such PEG linkers are commonly used to tune the spatial separation and relative orientation between the ligand that recruits an E3 ligase and the ligand that binds the target protein, thereby optimizing ternary complex formation and degradation potency. The terminal carboxyl group enables robust amide or ester bond formation to attach the linker to other PROTAC fragments under standard coupling conditions, making it a practical building block for systematic linker-length and geometry studies.
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* For research and manufacturing use only. Not for human or clinical use.
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Fmoc-NH-PEG25-CH2CH2COOH is a PEG-based bifunctional linker designed for constructing PROTACs and related targeted protein degradation conjugates. Its architecture combines an orthogonally protected amine for controlled coupling with a terminal carboxylic acid for attachment to a ligand or warhead, while the PEG segment provides conformational flexibility and improved solubility. The molecule is widely used in stepwise synthetic workflows; detailed structural and reactivity considerations are provided below.
Structure: The linker contains an Fmoc-protected amine linked to a poly(ethylene glycol) chain, terminating in a flexible ethylene spacer and a carboxylic acid. It features aromatic carbamate protection, ether-rich PEG segments, and aliphatic carbon–carbon and carbon–oxygen linkages, yielding a polar, water-compatible scaffold.
Reactivity: The terminal carboxylic acid can be activated for amide-bond formation with amine-bearing ligands using standard coupling chemistries such as carbodiimide reagents with additives or uronium/phosphonium activators. The Fmoc group enables orthogonal deprotection under base to reveal the amine for subsequent coupling. Typical conditions use polar aprotic solvents and proceed via acyl-activation followed by nucleophilic substitution to form stable amide linkages.
* 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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