E-Maleimidocaproic acid hydrazide HCl
CAS No.: 175290-73-0
Cat No.: BP-502154
4.5 
E-Maleimidocaproic acid hydrazide HCl is a bifunctional linker reagent combining a maleimide group with a hydrazide functionality through a flexible caproic acid spacer. The maleimide moiety is designed for fast, chemoselective conjugation to thiol-containing ligands (e.g., cysteine residues or reduced thiols) via Michael addition, enabling stable thioether linkage formation. The hydrazide end provides a complementary reactive handle for coupling to carbonyl-containing partners, supporting assembly of PROTACs and related targeted degradation constructs where two recognition elements must be positioned with controlled flexibility. In PROTAC design, such linkers help tune the effective distance and orientation between the target-binding ligand and the E3 ligase recruiter, which can strongly influence ternary complex formation and degradation potency. This reagent is therefore valuable for researchers seeking modular, experimentally tractable synthesis routes to thiol-functionalized targeted protein degraders and for optimizing linker length and conjugation chemistry.
Structure of 175290-73-0
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E-Maleimidocaproic acid hydrazide HCl is a versatile PROTAC linker building block that combines a maleimide-derived electrophile with a hydrazide handle for robust, chemoselective conjugation strategies. Its design supports modular assembly of targeted protein degraders by enabling stable attachment to thiol-bearing ligands and orthogonal functionalization for subsequent coupling steps. The resulting linker architecture can improve synthetic flexibility and facilitate controlled construction of PROTACs; detailed structural and reactivity considerations are provided below.
Structure: The molecule contains a maleimide electrophile embedded in a caproic acid-derived spacer and terminates in a hydrazide functionality. It features amide and hydrazide linkages, conjugated unsaturation within the maleimide ring, and an HCl-associated salt form that enhances handling and solubility. The spacer provides conformational flexibility.
Reactivity: The maleimide group undergoes chemoselective Michael-type addition with thiols under mildly basic aqueous conditions, forming a stable thioether linkage suitable for conjugating cysteine-containing ligands. The hydrazide enables further coupling via acyl hydrazone formation or amide/semicarbazide-style derivatization depending on the chosen electrophile. Typical workflows use buffered aqueous media with controlled pH, and thiol-reactivity is managed by avoiding competing nucleophiles and oxidizing conditions.
* 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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