Fmoc-D-Lys(Boc)-OPfp

Fmoc-D-Lys(Boc)-OPfp is an Fmoc-protected D-lysine derivative bearing a Boc-protected ε-amino side chain and an OPfp ester leaving group on the carboxylate. The molecule contains a chiral lysine backbone with defined stereochemistry at the α-carbon, a bulky orthogonally protected side-chain amine, and an activated pentafluorophenyl ester that can undergo acyl transfer under peptide-coupling conditions. The combination of the Fmoc carbamate and Boc urethane enables stepwise protection strategies, while the OPfp group provides a reactive handle for rapid formation of amide bonds with nucleophiles. The presence of multiple protecting groups and a fluorinated leaving group makes the compound a practical intermediate for peptide building block preparation and downstream derivatization in both research and process-oriented synthetic workflows.

1. Peptide Coupling

Fmoc-D-Lys(Boc)-OPfp is applied in peptide synthesis where OPfp activation supports efficient formation of amide bonds during protected amino acid coupling. The Fmoc group provides orthogonal N-protection for iterative solid-phase or solution-phase assembly, while the Boc-protected ε-amine preserves lysine side-chain integrity during chain elongation. The OPfp ester can participate in acyl transfer to introduce the lysine residue with stereochemical fidelity, and subsequent Fmoc deprotection can restore the α-amine for further coupling cycles. Lysine-containing sequences prepared from this building block can be used to generate protected peptide intermediates for later side-chain functionalization and conjugation chemistry.

2. Side-Chain Functionalization

Fmoc-D-Lys(Boc)-OPfp supports amino acid modification workflows targeting lysine side-chain chemistry while maintaining controlled orthogonal protection. The Boc-protected ε-amine acts as a stable handle during initial peptide construction, allowing selective deprotection to reveal a nucleophilic primary amine for labeling, crosslinking, or attachment of solubilizing groups. The OPfp-activated carboxylate enables incorporation into peptide scaffolds prior to side-chain derivatization, which can be advantageous when downstream transformations require the lysine position to be defined in sequence. The resulting protected lysine-containing intermediates can be converted into functionalized peptides and peptidomimetic analogs for chemical biology studies and molecular design programs.

3. Protected Amino Acid Chemistry

Fmoc-D-Lys(Boc)-OPfp is used as a chiral, protected amino acid derivative in synthetic organic chemistry for building amide-linked intermediates with predictable protecting-group behavior. The orthogonal Fmoc and Boc protection pattern allows sequential deprotection strategies, where Fmoc removal exposes the α-amine without disturbing the ε-amine until Boc deprotection is performed. The OPfp ester functionality provides a defined electrophilic site for nucleophile capture, supporting preparation of peptide fragments, amino acid conjugates, and protected carboxamide intermediates. The stereochemically defined lysine core makes the compound suitable for chiral synthesis planning, including preparation of D-lysine-containing peptides and structured fragments used in SAR studies and fragment-based molecular design.

4. Bioconjugation Intermediates

Fmoc-D-Lys(Boc)-OPfp can serve in bioconjugation chemistry as a lysine incorporation reagent that positions a protected ε-amine for later conjugation steps. The activated OPfp ester enables coupling to amine-bearing partners to form amide linkages while the Boc group can be carried through early stages to prevent premature side-chain reactions. The Fmoc-protected α-terminus supports controlled assembly of peptide-like conjugates, after which orthogonal deprotection can generate a reactive lysine side chain for attachment of tags, affinity handles, or biomolecule-reactive moieties. Lysine-rich conjugation motifs derived from this building block can be used to generate analytical standards, labeled peptides, and chemically defined biomolecule constructs for biochemical research workflows.

5. Process Chemistry Intermediate

Fmoc-D-Lys(Boc)-OPfp is relevant to process chemistry and fine chemical synthesis as a manufacturable intermediate that integrates multiple protection elements into a single, activated building block. The OPfp ester provides a clear acylation handle for converting the carboxylate into amide products under coupling conditions, which can simplify downstream intermediate formation compared with less activated carboxylic acids. The orthogonal Fmoc/Boc protection scheme supports controlled stepwise processing, aligning with industrial synthetic planning where protecting-group stability and selective deprotection are key to reliable batch-to-batch conversion. The defined D-lysine stereochemistry and robust functional group set make the compound suitable for producing protected peptide fragments and lysine-containing intermediates used in specialty chemical production and applied peptide manufacturing pipelines.

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