Fmoc-D-cysteine is a protected amino acid derivative in which the amino group of D-cysteine is protected as a 9H-fluoren-9-ylmethoxycarbonyl (Fmoc) carbamate while the carboxylic acid remains present for coupling chemistry. The molecule contains a thiol side chain characteristic of cysteine, and the D stereochemical configuration is specified by the "D" designation, with the Fmoc group providing chemoselective protection of the α-amino functionality. Fmoc-D-cysteine is used as a building block for stepwise peptide synthesis and for preparing cysteine-containing peptide intermediates, where the protected amino group supports controlled assembly and the free thiol can be addressed for subsequent derivatization or disulfide-related structural studies.
CAT No: CP00626
Fmoc-D-cysteine is a D-configured cysteine derivative bearing a fluorenylmethoxycarbonyl (Fmoc) group on the α-amino function and a free carboxylic acid, providing a protected, peptide-compatible amino acid building block with defined stereochemistry at the α-carbon. The side chain contains a thiol group that can participate in disulfide formation, thioether alkylation, or selective oxidation, while the Fmoc carbamate enables standard base-labile deprotection during solid-phase peptide synthesis. The combination of an acid functionality and a protected amine supports controlled coupling chemistry, and the D stereocenter allows incorporation of non-proteinogenic chirality for stereochemical studies and peptidomimetic design. As a chiral amino acid intermediate, Fmoc-D-cysteine can be further functionalized or protected at the thiol to manage oxidation state and chemoselectivity in downstream synthesis.
1. Peptide Synthesis
Fmoc-D-cysteine is used in peptide synthesis workflows where Fmoc protection supports stepwise N-terminal construction and base-mediated deprotection without requiring harsh conditions that would disrupt the thiol chemistry. The α-carboxylic acid and Fmoc-carbamate architecture enable peptide coupling at the carboxylate to form amide bonds, while the D-configuration at the amino acid backbone provides stereochemical control for D-cysteine-containing sequences. The side-chain thiol can be managed through oxidation to disulfides or converted to thioether derivatives to match the desired peptide topology and stability. Resulting D-cysteine-containing peptides and peptide fragments can serve as research-grade building blocks for sequence-specific studies, peptide library generation, and peptidomimetic scaffolds.
2. Side-Chain Functionalization
Fmoc-D-cysteine serves as a chemical handle for side-chain functionalization strategies that exploit the thiol reactivity for thioether formation, conjugation-ready intermediates, and redox-responsive motifs. The free thiol can be selectively oxidized to disulfides or protected as a thiol-protecting group to prevent premature oxidation during multi-step synthesis, while the Fmoc group provides orthogonal control over N-deprotection timing. The presence of both a protected amine and a carboxylic acid enables sequential derivatization where thiol chemistry can be tuned without losing peptide-coupling capability. Downstream products include cysteine-based linkers, redox-active conjugates, and functional amino acid derivatives used to generate chemically defined biomolecule conjugates and synthetic intermediates.
3. Chemical Biology Conjugation
Fmoc-D-cysteine is applied in chemical biology and biomolecule modification contexts where the thiol group supports site-directed conjugation chemistry and the D stereocenter helps tune stability against proteolysis. The Fmoc-protected amine allows controlled incorporation into peptide tags, while the carboxylic acid and thiol functionality enable formation of defined linkages to proteins, peptides, or polymeric carriers after appropriate deprotection and thiol state management. Thiol-to-maleimide, thiol-to-activated ester, or thiol-to-disulfide exchange routes can be used to generate conjugates with controlled attachment geometry, and D-cysteine incorporation can help maintain structural integrity in conjugate designs. Resulting labeled or functionalized biomolecular constructs can be used for mechanistic probing, binding studies, and analytical reagent preparation.
4. Peptidomimetics And SAR Studies
Fmoc-D-cysteine is suitable for peptidomimetic construction and structure-activity relationship studies where stereodefined D-amino acid incorporation modulates backbone conformation and side-chain orientation. The thiol side chain can be converted into thioether, disulfide, or other sulfur-containing motifs to probe how sulfur oxidation state and nucleophilicity influence molecular recognition. The Fmoc-protected α-amino group supports consistent peptide-like assembly, enabling systematic variation of sequence position and functional group identity in analog series. Synthesized D-cysteine-containing analogs can be used as chemically defined SAR probes and fragment-like components in iterative medicinal chemistry and molecular design campaigns.
5. Pharmaceutical Intermediate Preparation
Fmoc-D-cysteine is used as a process-relevant amino acid intermediate for manufacturing routes that require protected amino acid building blocks compatible with peptide coupling and controlled deprotection steps. The Fmoc carbamate provides a predictable N-protecting strategy for solid-phase or solution-phase peptide assembly, while the free carboxylic acid supports conversion to activated coupling forms under standard peptide-manufacturing conditions. The D stereochemistry and thiol functionality can be carried through as a defined chiral motif, with thiol protection or oxidation-state control enabling downstream formation of disulfide-containing products or thiol-derived derivatives. Resulting intermediates support fine chemical synthesis of D-cysteine-containing peptides, peptidomimetic fragments, and sulfur-functional drug-discovery chemistry materials.
6. Analytical Research Standards
Fmoc-D-cysteine is employed in analytical research settings as a stereochemically defined reference material for method development and characterization of cysteine-containing peptides and thiol-containing conjugates. The Fmoc group and D-configuration provide unambiguous structural markers that can assist in LC-MS identification, derivatization-based quantification, and monitoring of thiol oxidation or disulfide formation during sample preparation. The thiol functionality enables assay-compatible derivatization approaches when thiol state must be captured reproducibly, while the protected amino acid framework supports consistent behavior across peptide coupling and deprotection workflows. Generated analytical standards and calibration components can improve traceability for amino acid and peptide analysis, including thiol preservation and stereochemical assignment in complex matrices.
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