ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is a maleimide-functionalized ε-aminocaproic acid derivative bearing a phenyl ester linked to a 2-nitro-4-sulfonated aromatic ring and present as a sodium salt. The molecule combines a chiral-capable amino acid scaffold with a highly reactive maleimide electrophile, a pendant carboxylate/ester motif that can be hydrolyzed or transformed under controlled conditions, and a strongly electron-withdrawing nitro group alongside a sulfonate for aqueous compatibility. The maleimide ring can undergo selective Michael-type addition with thiols, while the sulfonate and phenyl ester framework support conjugation, labeling, and downstream analytical readouts. The overall reactivity profile makes the compound suitable as a chemically defined bioconjugation intermediate and as a functional tag precursor for peptide and protein modification workflows.

1. Bioconjugation Chemistry

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is applied in chemical biology and bioconjugation workflows where thiol-reactive maleimide chemistry enables controlled coupling to cysteine-containing peptides, engineered proteins, or thiolated linkers. The ε-amidocaproic acid spacer positions the maleimide for conjugation while the phenyl ester and sulfonate-bearing aromatic group provide a handle for solubility management and analytical tracking. The sodium sulfonate form supports aqueous handling, and the phenyl ester motif can be leveraged to tune stability prior to conjugation or subsequent deprotection/hydrolysis steps. Downstream derivatives can serve as labeled bioconjugates for binding assays, proteomics sample preparation, and reagent generation for molecular recognition studies.

2. Peptide Synthesis Coupling

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is suitable for peptide chemistry as a functionalized amino acid building block or side-chain modification reagent that can be incorporated into peptide scaffolds through amide/ester-compatible synthetic strategies. The caproic acid backbone provides a flexible aliphatic spacer that can separate the maleimide adduct from the peptide core, reducing steric interference during coupling and improving accessibility for subsequent thiol addition. The maleimide electrophile can be installed as a protected or late-stage functionality depending on the protecting-group strategy used in the peptide synthesis route, while the sulfonated aromatic group can function as a spectroscopic or mass-tagging element. The resulting peptide conjugates can be used for structure-activity relationship studies, peptide display formats, and chemically defined construct generation in applied peptide science.

3. Drug Discovery Labeling

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is employed in drug discovery research as a chemical probe scaffold for labeling cysteine residues and mapping interaction sites on target proteins. The combination of a thiol-reactive maleimide and an anionic sulfonate-bearing aromatic fragment supports reagent design for aqueous assay conditions and can facilitate separation or detection by orthogonal analytical methods. The phenyl ester functionality may be used as a tunable stability element, enabling controlled release or transformation to generate labeled analogs for downstream characterization. The compound can be applied to probe-dependent studies, fragment-to-lead validation workflows, and SAR-oriented generation of covalent or semi-covalent chemical probes without altering the fundamental amino acid-based linker geometry.

4. Analytical Research Standards

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is appropriate for analytical research and method development where the nitro-sulfonated aromatic system and maleimide moiety support traceable derivatization chemistry. The sulfonate group enhances water compatibility, while the phenyl ester and nitro substituent can contribute to detectable signals under UV/visible or mass spectrometric workflows after conjugation or controlled hydrolysis. The maleimide electrophile enables quantitative tagging of thiols, allowing construction of calibration reagents, derivatization standards, and assay controls for thiol-containing analytes. Downstream use includes preparing labeled standards for chromatography calibration, monitoring conjugation efficiency in peptide/protein labeling experiments, and supporting quality-by-design documentation in fine chemical synthesis.

5. Process Chemistry Intermediate

ε-N-Maleimidocaproic acid-(2-nitro-4-sulfo)-phenyl ester sodium salt is relevant to process chemistry and specialty chemical production as a defined, functionalized intermediate for manufacturing thiol-reactive conjugation reagents. The structure integrates a stable maleimide-bearing linker framework with an anionic sulfonate that can improve handling in aqueous workups and facilitate salt formation control during scale-up. The phenyl ester provides a chemically addressable functional group that can be transformed to adjust solubility, stability, or coupling kinetics in downstream reagent synthesis. The compound can be incorporated into manufacturing routes for bioconjugation kits, labeling reagents, and peptide/protein modification consumables, aligning amino acid derivative chemistry with industrially practical intermediate design.

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