COOH-PEG6-COOtBu
CAS No.: 2093153-84-3
Cat No.: BP-500837
Purity: ≥95%
4.5 
COOH-PEG6-COOtBu is a heterobifunctional polyethylene glycol linker bearing a terminal carboxylic acid and a second carboxyl group protected as a tert-butyl ester. Structurally, it provides a flexible, hydrophilic PEG chain of moderate length that spaces and orients two reactive handles, while the tert-butyl ester enables selective, orthogonal coupling strategies during PROTAC assembly. In targeted protein degradation workflows, this linker is used to connect a ligand or warhead to a complementary module (e.g., an E3 ligase binder or other targeting element) through amide or ester-forming chemistries, improving effective reach and reducing steric hindrance at the junction. Upon deprotection of the tert-butyl ester under standard conditions, the second carboxyl group becomes available for further conjugation or for generating a final PROTAC architecture. Its utility lies in enabling modular synthesis, tunable linker geometry, and improved solubility for experimental evaluation of degradation potency and selectivity.
Structure of 2093153-84-3
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COOH-PEG6-COOtBu is a polyethylene glycol-based bifunctional linker designed for constructing PROTACs that require solubilizing, flexible spacing between a ligand and an E3-recruiting or target-binding module. Its ether-rich PEG backbone helps tune conformational freedom and aqueous compatibility, while the orthogonally protected carboxyl functionality supports stepwise conjugation strategies. The following sections describe the molecule’s structural features and practical reactivity considerations for PROTAC assembly.
Structure: The linker contains a PEG chain featuring repeating ether linkages, flanked by carboxylic acid and a protected tert-butyl ester group. It includes ester and acid functional groups capable of controlled interconversion, with an overall flexible, hydrophilic scaffold that promotes solubility and reduced steric constraints.
Reactivity: The free carboxylic acid can be activated for amide or ester coupling using standard carboxyl-activation chemistries, enabling formation of stable PROTAC bonds to amine- or alcohol-bearing partners. The tert-butyl ester is typically cleavable under acid-promoted conditions to regenerate the carboxyl group for subsequent coupling. Common approaches employ coupling reagents and compatible solvents such as polar aprotic media, following established PROTAC linker conjugation principles.
* 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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