D-S-Methyl-cysteine is a D-configured, sulfur-methylated cysteine derivative in which the thiol side chain is converted to a thioether (S-CH3) while retaining the amino acid backbone with an α-amino group and a carboxyl group. The molecule bears a carboxyl functionality suitable for salt formation or esterification and an amino group that can be protected or used for coupling chemistry, with the thioether side chain providing reduced thiol reactivity relative to unmodified cysteine. D-S-Methyl-cysteine is employed in peptide and amino-acid derivative synthesis and in chemical biology or analytical studies where a cysteine-like scaffold with a methylated sulfur substituent is required for structure-activity comparisons, labeling strategies, or controlled side-chain chemistry.
CAT No: CP08103
D-S-Methyl-cysteine is a D-configured cysteine derivative in which the thiol side chain is S-methylated, giving a thioether rather than a free thiol while retaining the amino acid backbone with a stereogenic center at the alpha carbon. The molecule bears a primary amine and a carboxylic acid (or acid form depending on handling), enabling standard amino acid coupling chemistry while modulating nucleophilicity and oxidative sensitivity through thioether substitution. The D-stereochemistry supports stereochemically defined incorporation into peptide-like frameworks and chiral intermediate sequences, and the sulfur methyl group provides a handle for controlled oxidation state changes and downstream functional group interconversion. As a chiral amino acid intermediate and side-chain-modified building block, D-S-methyl-cysteine can be used to access thioether-containing analogs, stereodefined cysteine surrogates, and sulfur-functional derivatives for synthetic and analytical workflows.
1. Peptide Synthesis
D-S-Methyl-cysteine is applied in peptide synthesis workflows where a cysteine-like residue is required without a free thiol, and the S-methyl thioether helps reduce side reactions during coupling and purification. The amino acid backbone with an alpha-amino group and carboxylic acid participates in standard amide bond formation after appropriate N- and C-terminal protection strategies, while the thioether side chain remains chemically stable under many peptide coupling conditions. D-stereochemical control supports the construction of stereodefined peptide segments and can be used to prepare cysteine analogs for mapping how sulfur substitution influences conformational preferences and chemical stability. Downstream, the resulting thioether-containing peptides can serve as intermediates for further sulfur oxidation, crosslinking chemistry, or comparative studies of cysteine-reactive analogs.
2. Side-Chain Functionalization
D-S-Methyl-cysteine is suitable for side-chain functionalization strategies that target sulfur chemistry while avoiding the high reactivity of free thiols. The S-methyl thioether can undergo controlled oxidative transformations to sulfoxide or sulfone motifs, enabling access to sulfur oxidation-state analogs that retain the D-amino acid stereocenter. The carboxyl and amine functionalities can be protected orthogonally during derivatization, allowing selective manipulation of the thioether side chain without perturbing the backbone. The resulting sulfur-modified amino acid derivatives can be carried into peptidomimetic construction, fragment elaboration, or chemical biology probes where thioether-to-oxidized sulfur transitions are used to tune polarity and reactivity.
3. Chiral Building Block Development
D-S-Methyl-cysteine functions as a chiral amino acid intermediate for stereoselective synthesis routes that require a D-configured cysteine surrogate. The alpha-chiral center and persistent amino acid functionality support its use in enantiopure sequences, including preparation of N-protected amino acid derivatives for iterative coupling steps. The S-methyl substitution provides a stable sulfur-containing stereochemical element that can be carried through multi-step fine chemical synthesis, including routes that later introduce additional functionality at sulfur through oxidation or substitution chemistry. The compound's defined stereochemistry and sulfur handle make it compatible with chiral intermediate supply chains for research-grade peptide building block preparation and downstream synthesis of stereochemically defined thioether-containing scaffolds.
4. Chemical Biology Probes
D-S-Methyl-cysteine is used in chemical biology research contexts where sulfur-containing amino acid analogs are needed to probe reactivity patterns and molecular recognition without thiol-based labeling. The thioether side chain can serve as a controlled sulfur motif that may be oxidized in situ or during synthetic preparation to generate sulfoxide/sulfone species for mechanistic studies and structure-function comparisons. The amino acid backbone supports conjugation strategies to biomolecule scaffolds after protection and activation, while the D-configuration can be used to evaluate stereochemical effects on binding or processing in enzyme assays. The resulting derivatives can be incorporated into labeling reagents, affinity handles, or peptide-based probes that emphasize sulfur chemistry modulation rather than direct thiol capture.
5. Analytical Standards
D-S-Methyl-cysteine is employed for analytical research and method development where stereochemically defined, sulfur-substituted cysteine analogs are required as reference materials. The presence of an amino acid backbone with a stable thioether side chain supports reproducible chromatographic and mass spectrometric behavior relative to free cysteine and other sulfur oxidation states. The D-stereochemical identity enables calibration and identification in workflows that distinguish enantiomeric or diastereomeric amino acid derivatives, particularly when sulfur oxidation state is part of the analytical question. The compound can be used to generate calibration sets, internal standards, or derivatized reference compounds that support reliable quantitation of cysteine-related species in synthetic monitoring and biochemical sample analysis.
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