Fmoc-L-Cys(Palm)-OH is an Fmoc-protected L-cysteine derivative bearing a Palm (palmitoyl) thioether protecting group on the cysteine side chain, classifying it as a protected, sulfur-functional amino acid used for peptide chemistry. The molecule contains an Fmoc carbamate on the α-amino group and a free carboxylic acid, while the side-chain sulfur is masked as a thioester-derived Palm group that modulates nucleophilicity and chemoselectivity during coupling and deprotection steps. In solid-phase peptide synthesis and related stepwise peptide assembly workflows, it provides a controlled cysteine handle for generating peptides with protected thiol chemistry and for minimizing undesired side reactions from the native cysteine thiol functionality.
CAT No: CP26063
CAS No:824955-27-3
Chemical Name:N-alpha-(9-Fluorenylmethyloxycarbonyl)-S-t-palmitoyl-L-cysteine
Fmoc-L-Cys(Palm)-OH is an Fmoc-protected L-cysteine derivative bearing a palmityl (Palm) thioether protecting group on the side-chain sulfur, yielding a chiral amino acid building block with a defined stereocenter at the alpha carbon. The molecule contains an Fmoc carbamate for orthogonal N-protection during solid-phase or solution peptide assembly, alongside a carboxylic acid handle that supports controlled coupling to activated amino acid derivatives. The thioether sulfur is masked as a stable S-alkyl group, modulating nucleophilicity and reducing undesired side reactions such as oxidation or thiol-mediated crosslinking during peptide synthesis. The combination of a protected amine, protected side-chain sulfur, and free carboxyl group makes the compound a practical intermediate for peptide construction, cysteine side-chain functionalization, and downstream synthetic transformations.
1. Peptide Synthesis
Fmoc-L-Cys(Palm)-OH is used in peptide synthesis workflows where orthogonal N-protection and controlled cysteine chemistry are required. The Fmoc group enables stepwise N-deprotection under base-promoted conditions, while the carboxylic acid participates in peptide coupling to form amide bonds with incoming amino acid residues. The Palm thioether protection suppresses thiol reactivity during chain elongation, supporting cleaner coupling sequences and minimizing side-chain oxidation or disulfide scrambling. The resulting cysteine-containing peptide intermediates can be carried forward for later side-chain deprotection and selective derivatization, aligning with peptide building block preparation and cysteine-rich sequence assembly strategies.
2. Side-Chain Functionalization
Fmoc-L-Cys(Palm)-OH supports amino acid derivatization programs focused on cysteine side-chain modification from a protected sulfur starting point. The thioether-protected sulfur can be converted into reactive thiol or thiol-equivalent functionality through appropriate deprotection or functional group interconversion, enabling subsequent conjugation to electrophiles, maleimide handles, or haloacetamide-type reagents used in bioconjugation chemistries. The Fmoc-protected alpha-amine and carboxylic acid allow the compound to be incorporated into peptide or small-molecule scaffolds before side-chain activation, preserving chemoselectivity across multi-step sequences. Downstream products include cysteine-functional peptides, redox-responsive linkers, and sulfur-bearing intermediates that maintain stereochemical integrity of the L-cysteine backbone.
3. Bioconjugation Chemistry
Fmoc-L-Cys(Palm)-OH is applicable to chemical biology and materials-oriented bioconjugation strategies that require cysteine-compatible coupling sites with controlled oxidation state. The masked side-chain sulfur reduces premature thiol oxidation during synthesis of cysteine-bearing conjugates, while the Fmoc-protected amine and carboxyl functionality facilitate incorporation into peptide linkers or handle-bearing constructs. Side-chain activation after peptide or linker assembly can enable site-selective attachment to biomolecule surfaces, polymer backbones, or affinity tags through thiol-reactive electrophiles. The compound thus functions as a chiral cysteine intermediate for generating conjugation-ready building blocks used in biomolecule labeling and linker design.
4. Process Chemistry Intermediate
Fmoc-L-Cys(Palm)-OH can be employed as a manufacturing intermediate in fine chemical synthesis where stable protecting-group behavior supports scalable peptide building block preparation. The Fmoc carbamate provides robust N-protection during coupling operations, and the Palm thioether offers a sulfur-protection strategy that can reduce side reactions associated with free thiols under typical peptide-processing conditions. The presence of a single carboxylic acid group enables predictable activation chemistry for producing amide-forming intermediates, supporting reproducible downstream conversion into cysteine-containing derivatives. The compound's defined stereochemistry and orthogonal protection pattern make it suitable for process chemistry routes that require consistent intermediate quality for peptide analog construction and industrial intermediate preparation.
5. Peptidomimetics And SAR Studies
Fmoc-L-Cys(Palm)-OH is suitable for peptidomimetic and structure-activity relationship (SAR) studies that incorporate cysteine residues or cysteine-mimicking motifs into bioactive scaffolds. The Fmoc-protected amino acid form supports sequential assembly into peptide analogs, while the protected sulfur enables controlled introduction of sulfur functionality at a defined position within a molecular framework. The chirality of the L-cysteine backbone can be retained through peptide coupling and subsequent transformations, supporting stereochemically defined analog libraries for SAR-driven optimization of binding or stability properties. The compound can also serve as a starting point for generating diversified cysteine-bearing fragments used in molecular design and comparative SAR workflows.
6. Analytical Research Standards
Fmoc-L-Cys(Palm)-OH can be used in analytical research settings as a reference material for method development and characterization of cysteine-containing peptide intermediates. The combination of Fmoc and Palm-protected sulfur yields a well-defined mass signature and predictable fragmentation behavior, which can assist LC-MS or MS/MS method tuning for protected cysteine species. The free carboxylic acid and protected functional groups enable consistent derivatization or coupling in analytical workflows that require controlled chemoselectivity. The compound therefore supports accurate monitoring of peptide coupling steps, protecting-group stability, and side-chain integrity during synthetic characterization of cysteine-bearing molecules.
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