D-Cysteine hydrochloride is the hydrochloride salt form of the sulfur-containing amino acid cysteine in the D stereochemical configuration, featuring a thiol-bearing side chain attached to the α-carbon along with an amino group and a carboxyl group. The molecule exists as the protonated chloride salt, with the α-amino and carboxyl functional groups enabling zwitterionic behavior in solution while the side-chain thiol can undergo reversible redox chemistry and participate in thiol-disulfide exchange under appropriate conditions. As a free amino acid salt, it is used as a defined cysteine source for peptide synthesis workflows, for preparing cysteine-containing amino acid derivatives, and for analytical or labeling studies where the D-configuration and thiol functionality are relevant.
CAT No: CP00605
CAS No:32443-99-5
Synonyms/Alias:D-Cysteinehydrochloride;32443-99-5;D-CYSTEINEHCL;(s)-2-amino-3-mercaptopropanoicacidhydrochloride;H-D-Cys-OH.HCl;H-D-Cys-OH.H2O.HCl;d-cyshhcl;h-d-cys-ohhcl;PubChem16838;D-2-Amino-3-MercaptopropionicAcidHydrochloride;AC1L3V4M;KSC222G6L;SCHEMBL730594;CTK1C2365;D-cysteine,hydrochloridehydrate;IFQSXNOEEPCSLW-HSHFZTNMSA-N;MolPort-003-929-582;EINECS251-043-9;ANW-59177;MFCD00150051;NSC742579;AKOS015892730;AC-7471;AM81652;AN-1397
D-Cysteine hydrochloride is the hydrochloride salt of the D-enantiomer of cysteine, featuring a chiral α-amino acid framework with a side-chain thiol (-SH) and a protonated amino group under salt conditions. The molecule combines an amino functionality, a carboxylic acid (or carboxylate under base), and a reactive sulfhydryl that can participate in nucleophilic substitution, oxidation to disulfides, and thiol-metal coordination. Salt formation improves handling and aqueous compatibility, while the stereochemical integrity of the D-configuration supports enantiospecific synthesis and downstream incorporation into chiral peptide and biomolecule contexts. The thiol's reactivity also makes it a practical precursor for protected cysteine derivatives and for converting into thioether, thioester, or disulfide-linked constructs used in peptide chemistry and biochemical labeling workflows.
1. Peptide Synthesis
D-Cysteine hydrochloride is used in peptide building workflows where a D-configured cysteine residue is required for stereodefined peptide coupling and conformational control. The amino and carboxyl functionalities enable conversion into activated coupling partners or protected amino acid derivatives, while the side-chain thiol can be managed through protection or controlled oxidation states to prevent side reactions during amide bond formation. The hydrochloride salt form supports preparation of N-protected cysteine intermediates and subsequent peptide coupling strategies that preserve the D-stereocenter. Downstream, D-cysteine-containing peptides and peptide fragments can be generated for structure-function studies, disulfide patterning, and stereochemically defined peptidomimetic scaffolds.
2. Bioconjugation Chemistry
D-Cysteine hydrochloride serves as a thiol source for bioconjugation and chemical biology applications that rely on controlled sulfhydryl reactivity. The free thiol can be converted into disulfide-linked conjugates, thioether linkers, or activated thiol intermediates suitable for coupling to maleimides, haloacetamides, or electrophilic handles on biomolecules. Salt-state handling supports aqueous or buffered derivatization conditions, and the D-configuration can be used to tune stability and recognition in chiral labeling contexts. Resulting D-cysteine-derived conjugates can function as labeling handles, crosslinking components, or linker units in biomolecule modification and analytical assay development.
3. Chiral Building Block Synthesis
D-Cysteine hydrochloride functions as a chiral amino acid intermediate for constructing enantioenriched sulfur-containing motifs in synthetic organic chemistry. The combination of a stereogenic α-carbon with a thiol side chain enables stereospecific transformation into N-protected cysteine derivatives, thioether analogs, and disulfide-forming intermediates while maintaining the D-configuration. Protecting-group strategies typically leverage thiol protection and selective deprotonation of the amino acid functionalities to support sequential functionalization without racemization. Downstream products include chiral intermediates for peptidomimetics, sulfur heterocycle precursors, and industrial fine-chemical intermediates that require a defined stereochemical sulfur handle.
4. Pharmaceutical Intermediate Preparation
D-Cysteine hydrochloride is applied in pharmaceutical intermediate preparation where sulfur-containing amino acid derivatives are needed for medicinal chemistry and process-oriented synthesis. The amino acid backbone allows conversion into N-protected and C-terminally functionalized intermediates, supporting peptide-like coupling chemistry and incorporation into larger heteroatom-rich frameworks. The thiol can be transformed into protected thioethers or disulfide-compatible motifs that align with downstream synthetic sequences and impurity control in manufacturing routes. D-cysteine-derived intermediates can be used to generate chiral building blocks for active pharmaceutical ingredient synthesis, linker reagents, and stereodefined sulfur-functional scaffolds.
5. Analytical Standards And Assay Reagents
D-Cysteine hydrochloride is utilized for analytical research where enantiopure amino acid reference material and thiol-reactive standards are required. The hydrochloride salt improves reproducibility in sample preparation and supports consistent derivatization behavior for chromatographic or spectrometric detection of thiol-containing species. The D-enantiomeric identity enables enantioselective method development and validation in amino acid profiling, including workflows that distinguish D- and L-forms after derivatization. Thiol chemistry compatibility also supports preparing derivatized standards for monitoring oxidation state changes, disulfide formation, and conversion to thioether analogs during biochemical or process studies.
6. Side-Chain Functionalization
D-Cysteine hydrochloride is suitable for side-chain functionalization strategies that exploit the thiol's nucleophilicity and oxidation chemistry. The sulfhydryl can be selectively alkylated to form thioethers, oxidized to disulfides, or converted into thioester and thioamide-compatible intermediates through controlled derivatization sequences. The amino acid functionality supports orthogonal protection planning, enabling selective transformations at the thiol while the amino acid backbone is protected or activated for subsequent coupling. Downstream, functionalized D-cysteine derivatives can serve as intermediates for constructing sulfur-containing linkers, crosslinkers, and peptidomimetic elements used in applied synthetic methodology and industrial fine chemical production.
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