Fmoc-D-Lys(Nic)-OH

Fmoc-D-Lys(Nic)-OH is an Fmoc-protected D-lysine derivative bearing a side-chain nicotinyl (Nic) amide substituent on the ε-amino group, providing a defined chiral amino acid building block for peptide and medicinal chemistry workflows. The molecule contains a fluorenylmethyloxycarbonyl (Fmoc) carbamate on the α-amino group, a free carboxylic acid for C-terminal coupling chemistry, and a stereogenic center characteristic of the D-lysine backbone. The nicotinyl functionality introduces a heteroaromatic ring with nitrogen-containing coordination and hydrogen-bonding features, while the ε-nicotinamide-like substitution modulates nucleophilicity and directs selective transformations compared with unprotected lysine derivatives. The combination of orthogonal protection (Fmoc on the α-amine) and a side-chain heteroaryl group makes the compound suitable for controlled peptide assembly, fragment elaboration, and downstream derivatization in synthetic and biochemical research.

1. Peptide Synthesis

Fmoc-D-Lys(Nic)-OH supports solid-phase peptide synthesis and automated peptide assembly where D-lysine stereochemistry and a heteroaryl side chain are required for sequence-defined analogs. The Fmoc carbamate enables standard base-labile deprotection to expose the α-amine for peptide coupling, while the free carboxylic acid participates in amide bond formation to the next residue under peptide coupling conditions. The ε-nicotinyl substitution remains compatible with many peptide synthesis cycles, allowing the nicotinyl side chain to be carried through as a functional handle for later conjugation, coordination, or binding studies. Incorporation of this protected D-lysine into peptide building blocks facilitates the generation of D-amino acid-containing peptides and peptidomimetic scaffolds with altered protease recognition and defined side-chain electronics.

2. Side-Chain Functionalization

Fmoc-D-Lys(Nic)-OH is suitable for side-chain functionalization strategies that leverage the nicotinyl heteroaromatic ring as a functional motif. The lysine scaffold provides a spatially separated ε-substituent position, and the Nic group introduces nitrogen atoms that can participate in metal coordination, pH-dependent hydrogen bonding, and heteroaromatic reactivity patterns distinct from aliphatic lysine side chains. Orthogonal protection via the Fmoc group allows selective α-amino chemistry during peptide coupling, while the side-chain nicotinyl substitution can be retained for post-assembly derivatization or used as a stable directing group in medicinal chemistry intermediate construction. Downstream transformations can include conversion of the heteroaryl-containing peptide or intermediate into conjugates, affinity probes, or SAR-focused analog series where side-chain identity is the primary structural variable.

3. Chemical Biology Probes

Fmoc-D-Lys(Nic)-OH can be employed in chemical biology workflows that require defined stereochemistry and a heteroaryl functional group for molecular recognition studies. The D-lysine backbone contributes a stereochemical element that can modulate binding modes and proteolytic stability in peptide-based probes, while the nicotinyl side chain provides a nitrogen-rich aromatic surface for hydrogen-bonding and coordination interactions. Fmoc protection supports incorporation into peptide tags, enabling controlled presentation of the heteroaryl motif on a biomolecule-binding scaffold during synthesis. Resulting D-lysine-containing peptide probes can be used as research intermediates for target engagement studies, receptor/ligand binding investigations, and structure-driven design of functional biomolecular tools.

4. Drug Discovery SAR Studies

Fmoc-D-Lys(Nic)-OH is applicable to structure-activity relationship studies in medicinal chemistry where lysine-derived motifs and heteroaryl side chains are systematically varied. The presence of a single, stereochemically defined D-lysine center enables consistent comparison across analogs, while the nicotinyl substituent provides a chemically interpretable handle for tuning polarity, aromatic stacking, and heteroatom-mediated interactions. Fmoc deprotection and peptide coupling compatibility allow this building block to be integrated into larger peptidomimetic or peptide-like series, supporting iterative synthesis of analogs with controlled side-chain identity. Downstream, the resulting intermediates can be further elaborated into fragment-linked structures, constrained scaffolds, or purified SAR candidates where the D-lysine and nicotinyl features remain structurally anchored.

5. Pharmaceutical Manufacturing Intermediates

Fmoc-D-Lys(Nic)-OH is suitable as a manufacturing-oriented intermediate for producing D-amino acid-containing peptide intermediates and heteroaryl-functionalized building blocks used in specialty chemical and pharmaceutical supply chains. The Fmoc-protected α-amino group provides a well-defined, base-labile protection strategy that aligns with common peptide manufacturing workflows, while the free carboxylic acid supports reliable C-terminal coupling chemistry during stepwise assembly. The side-chain nicotinyl substitution offers a stable heteroaryl functionality that can be carried through manufacturing steps without requiring ε-amino re-protection, simplifying route design for heteroaryl-bearing peptide products. Utilization in controlled intermediate preparation supports downstream purification and conversion steps that depend on predictable functional group behavior typical of protected amino acid synthesis and peptide construction.

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