Fmoc-Cys(Acm)-OPfp

Fmoc-Cys(Acm)-OPfp is an Fmoc-protected cysteine derivative bearing an Acm-protected thiol and an OPfp ester at the carboxylate, forming a chiral amino acid intermediate with a protected side chain suitable for peptide and conjugation chemistry. The molecule contains a fluorenylmethoxycarbonyl (Fmoc) group on the α-amino function, an acetamidomethyl (Acm) thio-protecting group that preserves the cysteine sulfur in a masked, non-oxidizing state, and a pentafluorophenyl (OPfp) activated ester that enables acyl transfer under mild nucleophilic conditions. The stereogenic center of cysteine is retained through the synthesis of the protected building block, supporting stereochemically defined peptide assembly and downstream fragment coupling. The combination of orthogonal protecting groups and an activated carboxylate makes Fmoc-Cys(Acm)-OPfp a structurally coherent intermediate for protected amino acid synthesis, peptide coupling, and cysteine-selective functional transformations.

1. Peptide Synthesis

Fmoc-Cys(Acm)-OPfp supports solid-phase peptide synthesis and solution-phase peptide coupling workflows where cysteine residues require orthogonal protection to manage thiol reactivity during chain assembly. The Fmoc group enables standard base-labile deprotection to generate a reactive α-amino function for successive peptide bond formation, while the Acm thio-protection mitigates disulfide scrambling and side reactions during coupling cycles. The OPfp ester activates the carboxylate for nucleophilic acyl substitution, allowing formation of amide bonds with amine partners while maintaining the protected thiol for later selective unveiling. The resulting cysteine-containing peptide intermediates can be further processed into defined disulfide patterns or thiol-functionalized analogs, aligning with peptide building block preparation and peptide science requirements.

2. Cysteine-Selective Bioconjugation

Fmoc-Cys(Acm)-OPfp can be applied to chemical biology workflows that require controlled introduction of cysteine functionality into peptides, linkers, or biomolecule conjugates. The Acm-protected thiol functions as a stable handle during synthesis and purification steps, while the OPfp ester provides an activated acyl group for coupling to nucleophiles such as amines present on peptides or linker scaffolds. Orthogonal deprotection strategies allow the thiol to be revealed under conditions compatible with sensitive biomolecules, enabling subsequent thiol-directed conjugation chemistries without exposing free sulfur prematurely. The defined stereochemistry of the cysteine residue and the protected side-chain architecture help maintain structural fidelity in conjugate libraries used for biomolecule modification and molecular recognition studies.

3. Peptidomimetic Construction

Fmoc-Cys(Acm)-OPfp serves as a chiral cysteine-derived intermediate for peptidomimetic and structure-driven scaffold construction in synthetic organic chemistry. The Fmoc-protected amino functionality supports controlled incorporation into amide-rich frameworks, while the Acm group provides a masked thiol that can be converted into thioethers, sulfenamides, or disulfide-linked motifs after scaffold assembly. The OPfp activated ester can participate in fragment coupling to generate amide bonds that preserve the cysteine-derived stereocenter within larger heteroatom-containing motifs. Downstream transformation of the thiol after deprotection enables access to sulfur-containing pharmacophore mimics and cysteine-like reactive sites for SAR studies and molecular design programs.

4. Process Chemistry Intermediate

Fmoc-Cys(Acm)-OPfp is suitable for process chemistry intermediate preparation where orthogonal protecting groups and activated ester reactivity support scalable synthetic route design. The OPfp ester provides a predictable acyl-transfer reactivity profile for forming amide linkages, while the Fmoc group and Acm thio-protection allow staged deprotection and selective functional unveiling to reduce undesired side reactions. The protected, non-free thiol character can reduce oxidation and disulfide formation during manufacturing steps, supporting reproducible handling of cysteine-containing intermediates. The chiral amino acid backbone and protected side-chain arrangement make the compound compatible with downstream conversion into peptide building blocks, cysteine-containing fragments, and industrially relevant fine chemical intermediates.

5. Analytical Research Standards

Fmoc-Cys(Acm)-OPfp can be employed in analytical research for method development and reference material generation related to cysteine-containing protected amino acids and peptide fragments. The combination of Fmoc, Acm, and OPfp functionalities yields characteristic chromatographic and mass spectrometric signatures that assist in verifying protecting group integrity and monitoring coupling or deprotection steps. The defined stereochemistry and stable thio-protection support reproducible analytical comparisons across batches of protected cysteine derivatives and peptide intermediates. The compound's structure also enables targeted derivatization workflows to confirm thiol availability after orthogonal deprotection, supporting analytical characterization of cysteine-containing products in biochemical research and applied peptide chemistry.

6. Pharmaceutical Manufacturing

Fmoc-Cys(Acm)-OPfp fits pharmaceutical manufacturing contexts that require protected amino acid chemistry for producing cysteine-bearing peptide intermediates under controlled protection strategies. The Fmoc group supports stepwise assembly logic through base-labile deprotection, while the Acm thio-protecting group helps manage sulfur reactivity during repeated coupling and purification operations. The OPfp activated ester enables efficient amide formation with amine-containing partners, supporting the construction of well-defined intermediates used for further processing into final peptide or peptide-like materials. Orthogonal deprotection and subsequent thiol-directed transformations allow downstream generation of disulfide architectures or thiol-functionalized intermediates consistent with industrial peptide science and fine chemical production requirements.

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