DL-Cysteine hydrochloride monohydrate contains the amino acid skeleton with a thiol-bearing side chain, where the DL designation indicates a racemic mixture of cysteine stereoisomers and the molecule is present as a hydrochloride salt with one water of hydration. The compound bears a primary amino group and a carboxyl group while the side chain features a sulfhydryl (-SH) that can participate in redox chemistry and form disulfide-linked species under appropriate conditions, and the salt form provides the amino group in a protonated state. In biochemical and peptide-related workflows, it is used as a cysteine source for preparing cysteine-containing peptides and for chemical labeling, conjugation, or analytical derivatization that relies on the thiol functionality.
CAT No: CP00609
DL-Cysteine hydrochloride monohydrate contains the amino acid core with a thiol-bearing side chain and a protonated amino group associated with chloride, and it crystallizes with one equivalent of water as a monohydrate. The molecule presents a stereogenic center in the DL mixture, enabling access to both L- and D-derived cysteine chemistry for peptide and small-molecule synthesis workflows. The free thiol can be selectively protected or transformed, while the amino and carboxyl functionalities support salt formation, coupling chemistry, and downstream derivatization. As a chiral amino acid precursor and biochemical building block, it functions as a practical starting material for preparing protected cysteine derivatives, thiol-reactive reagents, and sulfur-containing intermediates used across synthetic and analytical programs.
1. Peptide Synthesis
DL-Cysteine hydrochloride monohydrate serves as a cysteine source for peptide building block preparation in solid-phase or solution-phase peptide synthesis. The amino acid backbone and carboxyl group enable conversion to N-protected cysteine derivatives suitable for amide bond formation, while the thiol side chain can be protected to control disulfide formation during coupling and deprotection. DL stereochemistry can be leveraged when racemic cysteine incorporation is acceptable for mechanistic studies, peptide library generation, or non-stereospecific scaffold construction. Downstream processing can yield cysteine-containing peptides, thioether analogs, or disulfide-structured intermediates that support peptide science and sulfur chemistry.
2. Chemical Biology Labeling
DL-Cysteine hydrochloride monohydrate supports chemical biology workflows that rely on thiol reactivity for conjugation and biomolecule modification. The side-chain thiol can be converted into activated forms or protected during synthesis, then reintroduced under controlled conditions to enable site-selective attachment strategies to proteins, peptides, or nucleophilic capture handles. DL mixtures can be used in screening contexts where stereochemical purity is not the primary determinant of labeling behavior, while still providing the sulfur nucleophile required for thioether formation or disulfide exchange chemistry. Resulting cysteine-derived linkers and thiol reagents can be applied to biomolecular probes, surface functionalization intermediates, and mechanistic studies of thiol-dependent interactions.
3. Protected Amino Acid Chemistry
DL-Cysteine hydrochloride monohydrate functions as a feedstock for protected amino acid synthesis, where thiol protection strategies are central to compatibility with peptide coupling and purification. The hydrochloride salt form facilitates handling and conversion to N-protected and/or carboxyl-activated derivatives, while the thiol can be masked as a stable protecting group to prevent oxidation and side reactions. Racemic stereochemistry provides access to both enantiomeric cysteine derivatives after resolution steps or stereospecific downstream transformations when required by the target route. Protected cysteine intermediates derived from this starting material can be used to construct thioether-containing analogs, disulfide precursors, and sulfur-functionalized peptide segments.
4. Analytical Standards Development
DL-Cysteine hydrochloride monohydrate can be employed in analytical research as a reference material for amino acid profiling and sulfur-species quantification. The defined amino acid structure with a thiol side chain enables calibration of chromatographic and spectrometric methods after derivatization to stabilize the thiol or to introduce a detectable tag. DL composition supports method development where total cysteine reactivity or thiol derivatization behavior is assessed without requiring enantiopure standards. Cysteine-derived derivatization products prepared from this material can serve as internal standards, method controls, or intermediate analytes for validating sample preparation and detection performance.
5. Process Chemistry Intermediate
DL-Cysteine hydrochloride monohydrate is suitable for process chemistry intermediate preparation in industrial fine chemical synthesis, particularly for routes that incorporate sulfur-containing functionality. The amino acid framework allows conversion into activated derivatives and thiol-protected intermediates that can be carried through multi-step manufacturing sequences while minimizing oxidative degradation of the thiol group. Salt formation with hydrochloride supports reproducible solids handling and can simplify downstream conversion to N-protected amino acid derivatives used in peptide-manufacturing supply chains. Sulfur-bearing intermediates derived from cysteine can further enable thioether formation, disulfide precursor generation, and specialty chemical production where sulfur functionality is required for reactivity control.
6. Thioether and Disulfide Building Blocks
DL-Cysteine hydrochloride monohydrate serves as a starting point for generating thioether and disulfide-related building blocks used in synthetic organic chemistry and peptidomimetic construction. The thiol side chain can be selectively transformed into thioether linkages or into disulfide-forming precursors, while the amino acid backbone can be protected or activated to integrate the sulfur motif into larger scaffolds. DL stereochemistry can be accommodated when the sulfur connectivity and functional-group placement dominate the structure-property relationship rather than absolute configuration. Resulting cysteine-derived intermediates can be incorporated into peptide analogs, sulfur-rich linkers, and conjugation-ready molecules that extend amino acid chemistry into applied molecular design.
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