Fmoc-N-PEG3-CH2-NHS ester
CAS No.: 2128735-25-9
Cat No.: BP-501638
4.5 
Fmoc-N-PEG3-CH2-NHS ester is an activated polyethylene glycol (PEG) linker designed for stepwise PROTAC and targeted-degradation construct synthesis. Structurally, it combines an Fmoc-protected amine handle with a short, three-unit PEG spacer terminated by a benzylamine-like methylene and an N-hydroxysuccinimide (NHS) ester, enabling efficient coupling to primary amines on ligands such as lysine-containing peptides or engineered protein-binding modules. The PEG3 segment provides conformational flexibility and improves aqueous solubility, while the NHS ester facilitates formation of stable amide bonds under standard bioconjugation conditions, allowing researchers to connect the linker to targeting and/or E3-ligase-binding components without requiring harsh chemistries. In PROTAC design, this modular linker helps tune spatial arrangement and reduces steric constraints between the two binding moieties, which can enhance ternary complex formation and degradation efficacy. Its reliable reactivity and straightforward synthetic compatibility make it a practical building block for constructing and optimizing linker architectures in targeted protein degradation research.
Structure of 2128735-25-9
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Fmoc-N-PEG3-CH2-NHS ester is a heterobifunctional PEG-based PROTAC linker building block designed to connect ligands through efficient amide-forming chemistry while retaining a protected, orthogonally removable Fmoc group for controlled assembly. Its PEG spacer supports favorable solubility and conformational flexibility, which can improve productive ternary complex formation in targeted protein degradation workflows. The points below describe the structure and practical reactivity considerations in detail.
Structure: The molecule contains an Fmoc-protected amine linked to a short PEG chain terminated by a benzylic methylene and an N-hydroxysuccinimide ester. It features amide and carbamate-compatible linkages, an aromatic fluorene-derived Fmoc group, and an activated carboxylate for nucleophilic acyl substitution.
Reactivity: The NHS ester undergoes acyl substitution with primary amines to form stable amide bonds under mildly basic, water-compatible conditions. Typical PROTAC synthesis strategies use an amine-bearing ligand (e.g., lysine- or amino-terminated handles) with the linker in polar aprotic or mixed aqueous media, often with base to promote nucleophilicity while minimizing hydrolysis. The Fmoc group is generally retained during coupling and can be removed under standard deprotection conditions when orthogonal functionalization is required.
* 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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