S-Bis-(PEG4-Boc)
Cat No.: BP-502105
4.5 
S-Bis-(PEG4-Boc) is a PEG-based, tert-butyl ester-protected bis-functional linker designed for constructing PROTACs and other targeted protein degradation conjugates. Structurally, it contains two PEG4 ethylene glycol segments connected through a sulfur-centered linkage, providing a flexible, hydrophilic spacer that can reduce steric constraints between the two binding modules of a PROTAC. The tert-butyl ester groups protect carboxyl functionalities that can be selectively deprotected and then activated for amide or related coupling chemistries, enabling attachment to ligands such as E3 ligase recruiters or target-binding warheads. In PROTAC design, this type of linker helps tune effective distance, conformational freedom, and overall solubility, which are critical for promoting productive ternary complex formation and subsequent ubiquitination-driven degradation. As a modular building block, S-Bis-(PEG4-Boc) is valuable for systematic linker optimization and for generating libraries of conjugates with consistent PEG-mediated spacing.
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* For research and manufacturing use only. Not for human or clinical use.
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S-Bis-(PEG4-Boc) is a PEG-based, bifunctional PROTAC linker building block designed to connect two reactive partners while providing conformational flexibility and improved solubility in common organic media. Its Boc-protected termini enable controlled, stepwise functionalization, supporting the modular assembly of targeted protein degraders. The linker’s ether-rich scaffold and protected amine/acid functionality are advantageous for tuning linker length, polarity, and coupling compatibility during PROTAC synthesis; detailed structure and reactivity considerations are provided below.
Structure: The molecule is a bis-functional PEG-derived scaffold bearing Boc-protected groups. It contains multiple ether linkages that impart flexibility and polarity, along with carbamate-type Boc functionalities that mask reactive sites. The overall architecture supports controlled presentation of coupling handles for PROTAC conjugation.
Reactivity: Boc-protected groups are typically deprotected under mild acid conditions to reveal the corresponding nucleophiles for subsequent coupling. Suitable PROTAC assembly steps often include amide or carbamate formation using activated carboxylic acids or appropriate electrophiles, followed by purification to remove protecting-group residues. Common approaches employ bases and coupling reagents compatible with PEG ether stability, with solvent systems selected to maintain solubility and minimize linker cleavage.
* 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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