Boc-PEG4-acid
CAS No.: 2244684-38-4
Cat No.: BP-501288
4.5 
Boc-PEG4-acid is a polyethylene glycol (PEG) linker bearing one free carboxylic acid and one tert-butyl ester-protected carboxylic acid, providing a chemically versatile, water-compatible chain for PROTAC synthesis. The PEG4 segment offers a flexible, hydrophilic spacer that can reduce steric interference between the ligand-binding moieties of a PROTAC, while maintaining sufficient conformational freedom for productive ternary complex formation. The terminal carboxyl group enables straightforward conjugation strategies, such as amide coupling or activation to form reactive intermediates for attachment to either the target-binding ligand or the E3 ligase recruiter, depending on the chosen synthetic route. In targeted protein degradation research, this linker helps tune linker length and polarity, which are key determinants of degradation potency and selectivity by influencing binding geometry and the residence time of the assembled complex. The tert-butyl ester provides orthogonal acid protection during stepwise synthesis, improving reproducibility when generating modular PROTAC constructs.
Structure of 2244684-38-4
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Boc-PEG4-acid is a PEG-based PROTAC linker building block designed to provide aqueous compatibility, conformational flexibility, and reliable functional-group handles for assembling targeted protein degraders. Its polyethylene glycol segment helps tune linker hydrophilicity and spatial presentation between the ligand and the recruited E3 ligase module, supporting efficient ternary complex formation. The structure and reactivity considerations for PROTAC synthesis are described in detail below.
Structure: Boc-PEG4-acid contains a polyethylene glycol chain bearing one free carboxylic acid and one carboxylic acid protected as a tert-butyl ester. It features ether linkages within the PEG backbone, a free carboxyl functionality, and a tert-butyl ester-protected carboxyl group, yielding a polar, water-tolerant scaffold suitable for bioconjugation chemistry.
Reactivity: The carboxylic acid enables standard linker-to-ligand coupling via amide bond formation, commonly using activating reagents such as carbodiimides with additives that suppress side reactions. The tert-butyl ester can be removed under controlled acidic conditions to expose the second carboxylic acid for subsequent coupling steps. Typical PROTAC assembly strategies rely on preserving PEG integrity and avoiding harsh conditions that could degrade sensitive ligand motifs. Appropriate solvents and mild bases are selected to maintain solubility and reaction selectivity.
* 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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