L-S-Methyl-cysteine is an amino acid derivative of cysteine in which the thiol side chain is S-methylated, retaining the α-amino and α-carboxyl functionality while converting the sulfur substituent from a free thiol to a thioether. The molecule bears an α-amino group and a carboxylic acid group, and its stereochemistry is indicated as L at the α-carbon, with the side-chain sulfur methyl substituent defining the S-methyl configuration. L-S-Methyl-cysteine is used in peptide and chemical biology workflows as a cysteine analogue to control thiol reactivity, support structure-activity studies, and enable incorporation or labeling strategies where a protected or non-thiol sulfur functionality is required.
CAT No: CP08102
L-S-Methyl-cysteine is a chiral sulfur-containing amino acid derivative in which the cysteine side chain bears a thioether methyl group, giving a stable, non-thiol sulfur functionality compared with native cysteine. The molecule contains a stereogenic center at the alpha carbon (L-configuration) and presents an amino group and a carboxylic acid, enabling salt formation and controlled reactivity during peptide-coupling or derivatization workflows. The thioether sulfur can participate in S-alkylation/oxidation chemistry and can be used as a handle for downstream functional group interconversion while maintaining a cysteine-like carbon skeleton. As an amino acid-based intermediate, L-S-Methyl-cysteine can be incorporated into synthetic sequences that require chiral sulfur chemistry, protected-amino-acid handling, and side-chain transformation for peptidomimetic or biochemical probe construction.
1. Peptide Synthesis
L-S-Methyl-cysteine is applied in peptide synthesis workflows where a cysteine analog with a thioether side chain is required to modulate oxidation sensitivity and disulfide formation behavior. The amino and carboxyl groups support peptide coupling chemistry after appropriate N-protection and, when needed, C-terminal activation, while the L-stereocenter provides stereochemical fidelity during amide bond formation. The S-methyl thioether can influence side-chain reactivity during coupling and subsequent deprotection steps, enabling controlled generation of sulfur-containing peptide analogs. Peptide building block preparation from L-S-Methyl-cysteine can serve fragment-based assembly of thioether-stabilized sequences for biochemical research and structure-activity relationship studies.
2. Amino Acid Derivatization
L-S-Methyl-cysteine is used for amino acid derivatization and chiral intermediate preparation in synthetic organic chemistry, leveraging the thioether sulfur as a functional handle. The side-chain thioether can undergo oxidation to sulfoxide or further sulfur functionalization under controlled conditions, while the amino and carboxyl functionalities can be protected to tune chemoselectivity. Derivatization strategies can target formation of activated esters, amide-linked conjugates, or protected amino acid derivatives that are compatible with peptide coupling reagents. Downstream, sulfur-modified products derived from L-S-Methyl-cysteine can be applied as intermediates for chiral sulfur chemistry, peptidomimetic scaffolds, and reagent development in applied synthesis.
3. Chemical Biology Probes
L-S-Methyl-cysteine is suitable for chemical biology research where cysteine-like positioning is needed without free thiol reactivity. The thioether sulfur provides a chemically distinct sulfur environment that can be used to control labeling stability, oxidation state, and conjugation selectivity in biomolecule modification contexts. The L-amino acid backbone enables incorporation into peptide mimics, linker units, or amino acid-based tags that maintain stereochemical recognition features relevant to molecular binding studies. The resulting sulfur-containing probes can support investigations of protein-ligand interactions, enzyme substrate preferences, and side-chain microenvironment effects in biochemical assays.
4. Pharmaceutical Intermediate Preparation
L-S-Methyl-cysteine is employed as a chiral amino acid intermediate in pharmaceutical intermediate preparation and fine chemical synthesis, particularly for routes that require sulfur-containing stereocenters. The presence of an alpha-amino acid framework supports conversion into N-protected derivatives and activated carboxyl equivalents for subsequent bond construction in medicinal chemistry synthesis. The S-methyl thioether can be retained to deliver a stable thioether motif or transformed into oxidized sulfur states as synthetic intermediates for heteroatom-functional scaffolds. Industrial process chemistry can apply L-S-Methyl-cysteine in scalable chiral building block strategies where controlled handling of amino and carboxyl groups is required for downstream API-adjacent synthesis.
5. Industrial Biocatalysis Feedstock
L-S-Methyl-cysteine can function as a feedstock for industrial biocatalysis and enzyme-enabled transformations that require a stable thioether-containing amino acid substrate. The L-configuration and amino acid functional groups allow enzymatic recognition in pathways that accept amino acid derivatives, while the non-thiol sulfur reduces susceptibility to disulfide scrambling during bioprocessing. The sulfur motif can be carried through enzymatic steps or used as a substrate for subsequent chemical conversion, enabling hybrid chemoenzymatic sequences. Downstream products from L-S-Methyl-cysteine can serve as intermediates for specialty chemical production and for manufacturing routes that integrate chiral amino acid chemistry with controlled sulfur functionalization.
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