Fmoc-L-Lys(Dansyl)-OH

Fmoc-L-Lys(Dansyl)-OH is an Fmoc-protected lysine derivative bearing a dansyl (5-dimethylaminonaphthalene sulfonyl) fluorophore on the side-chain ε-amino group. The molecule combines a stereodefined L-lysine backbone with a stable sulfonamide linkage to the dansyl chromophore, while retaining the Fmoc carbamate at the α-amino position for orthogonal peptide coupling. The carboxylic acid enables conversion into activated esters or coupling-ready derivatives, and the aromatic sulfonamide provides strong light-absorption and fluorescence for monitoring peptide assembly and downstream biomolecular interactions. The presence of the Fmoc group supports standard deprotection strategies, whereas the dansyl label remains chemically robust under typical peptide synthesis conditions, making the compound a chiral, fluorescent amino acid building block and analytical tag precursor.

1. Peptide Synthesis

Fmoc-L-Lys(Dansyl)-OH supports solid-phase peptide synthesis workflows where a fluorescent lysine side-chain is required for real-time sequence verification and post-synthetic characterization. The Fmoc-protected α-amino group participates in standard peptide coupling after base-mediated Fmoc removal, while the ε-amino is already functionalized as a dansyl sulfonamide, preventing uncontrolled side reactions during chain elongation. The carboxylic acid enables formation of activated intermediates compatible with amide bond formation, and the aromatic dansyl moiety can be used as a spectroscopic handle without introducing additional protecting-group manipulations on the lysine side chain. The resulting dansyl-containing peptides can be employed for peptide assembly studies, fragment ligation monitoring, and fluorescence-based quantification of coupling outcomes in peptide chemistry research and development.

2. Chemical Biology Labeling

Fmoc-L-Lys(Dansyl)-OH is suitable for chemical biology and biomolecular labeling strategies that require a lysine-positioned fluorophore with sulfonamide stability. The L-lysine stereochemistry and defined ε-linkage geometry position the dansyl group at a predictable distance from peptide backbone sites, enabling controlled probing of binding interfaces, conformational changes, and local microenvironment effects. The Fmoc group enables incorporation into peptides or peptide-like constructs, after which the dansyl label can function as a fluorescent reporter for receptor-ligand interactions, protein surface mapping, or nucleic-acid associated assemblies. The sulfonamide linkage and aromatic chromophore can also serve as a downstream intermediate for constructing dye-labeled biomolecule conjugates used in mechanistic studies and materials-oriented biochemical assays.

3. Bioconjugation Probes

Fmoc-L-Lys(Dansyl)-OH can be applied to bioconjugation chemistry where lysine-derived labeling is integrated into peptide scaffolds prior to conjugation to larger biomolecular targets. The compound's protected α-amino functionality supports peptide building block preparation, while the dansyl sulfonamide provides a stable, hydrophobic fluorescent tag that can be retained through purification and conjugation steps. The presence of a single, defined chromophore-bearing side chain can facilitate structure-function investigations by enabling systematic variation of labeling position within peptide or protein fragments. The resulting fluorescent constructs can be used as probes for binding kinetics, cellular uptake studies in assay formats, and analytical tracking of conjugate formation in applied biochemical research and specialty chemical development.

4. SAR Studies

Fmoc-L-Lys(Dansyl)-OH is applicable to structure-activity relationship studies in which fluorescent readouts are integrated into analog libraries to correlate sequence features with molecular recognition behavior. The lysine side-chain dansyl group provides an aromatic reporter that can be used to monitor changes in polarity, aggregation tendency, or binding-induced fluorescence shifts across analog series. The Fmoc-protected amino acid enables controlled incorporation into peptide analogs, supporting systematic variation of neighboring residues while maintaining a constant labeled side chain. The ability to prepare coupling-ready derivatives and generate labeled analogs supports iterative medicinal chemistry workflows focused on peptide-like scaffolds, fragment optimization, and SAR mapping using spectroscopic endpoints.

5. Pharmaceutical Manufacturing Intermediates

Fmoc-L-Lys(Dansyl)-OH can serve as a process chemistry intermediate for producing fluorescent reference standards, labeled internal controls, and characterization materials used during manufacturing of peptide-based drug substances or peptide intermediates. The Fmoc protection strategy aligns with common peptide synthesis manufacturing logic, where orthogonal deprotection and controlled amide bond formation are required to manage chemoselectivity on scale. The dansyl sulfonamide label is compatible with typical purification and analytical workflows, enabling robust traceability of peptide fragments and batch-to-batch comparability through fluorescence detection. The defined chiral lysine backbone and single-site labeling pattern support reproducible analytical characterization of peptide intermediates and finished labeled materials in industrial fine chemical production.

6. Analytical Research Standards

Fmoc-L-Lys(Dansyl)-OH is suitable for analytical research and method development where a fluorescent amino acid derivative is needed as a calibration component, LC/fluorescence reference, or peptide coupling monitor. The combination of an Fmoc-protected amino acid structure with a sulfonamide-linked dansyl chromophore yields a molecule with strong, easily detectable spectral properties that can be tracked during derivatization and purification. The carboxylic acid functionality supports conversion to defined derivatives for chromatographic behavior control, while the aromatic sulfonamide enables sensitive detection under fluorescence-based analytical conditions. The compound's stereodefined lysine framework also supports use in stereochemical and identity confirmation contexts for labeled peptide building blocks and peptide synthesis process monitoring in research-grade and industrial analytical laboratories.

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