H-D-Cys(Acm)-OH · HCl

H-D-Cys(Acm)-OH · HCl is a chiral cysteine derivative in which the thiol side chain is protected as an Acm thioamide/aryl-type thio-protecting group (Acm), while the α-amino functionality is present in the free amino acid form and the compound is supplied as the hydrochloride salt. The molecule therefore contains a defined stereocenter at the α-carbon, a carboxylic acid group for peptide coupling compatibility, and a masked sulfur nucleophile that remains stable under many peptide synthesis conditions. The Acm group can be selectively removed or transformed under controlled conditions, enabling controlled thiol unmasking for disulfide formation, thioether installation, or native cysteine mimic generation. Salt formation with HCl improves handling and solubility of the amino acid intermediate, supporting reproducible downstream conversion into protected peptide building blocks and synthetic intermediates.

1. Protected Amino Acids

H-D-Cys(Acm)-OH · HCl is used in protected amino acid synthesis and peptide building block preparation where side-chain thiol masking is required to prevent premature disulfide scrambling or side reactions during coupling. The carboxylic acid and amino groups provide the functional handles needed for standard peptide coupling chemistry, while the Acm-protected sulfur suppresses thiol reactivity during N-protection and amide bond formation steps. Selective Acm deprotection strategies can later reveal the cysteine thiol for controlled disulfide bond construction or thiol-based functionalization. The hydrochloride salt form also supports consistent intermediate handling in synthetic workflows that require reliable salt-to-free-base conversion prior to coupling.

2. Peptide Synthesis

H-D-Cys(Acm)-OH · HCl is applied as a cysteine residue precursor in peptide synthesis workflows that require orthogonal protection of sulfur relative to other side chains. The stereodefined H-D-Cys(Acm)-OH scaffold enables incorporation of a specific configuration at the α-carbon, supporting stereochemically controlled peptide assembly and producing peptide analogs with defined chiral environments. The Acm group functions as a stable protecting group during peptide chain elongation, and subsequent thiol unmasking can be used to generate disulfide-containing peptides or to install cysteine-derived linkers. Downstream, the resulting cysteine-bearing peptide fragments can be used for structure-activity relationship studies, folding investigations, and preparation of conjugatable peptide intermediates.

3. Bioconjugation Chemistry

H-D-Cys(Acm)-OH · HCl serves as a chemically addressable intermediate for bioconjugation strategies that rely on cysteine thiol chemistry after controlled deprotection. The protected thiol suppresses unwanted nucleophilic reactions during upstream synthesis of peptide tags, linkers, or protein-reactive fragments, while the carboxylic acid functionality supports conversion into activated derivatives for coupling to biomolecule scaffolds. Acm deprotection can generate a reactive thiol handle for conjugation chemistries such as disulfide exchange or thiol-selective ligation to electrophilic partners. The defined stereochemistry of the cysteine residue can be relevant when constructing biomolecule conjugates intended to preserve peptide recognition motifs or maintain stereochemical fidelity in linker regions.

4. Peptidomimetics And SAR

H-D-Cys(Acm)-OH · HCl is utilized in peptidomimetic construction and SAR-oriented molecular design where cysteine side-chain positioning and controlled sulfur chemistry influence receptor binding and conformational behavior. The amino acid backbone provides a stereochemically defined chiral center for incorporation into analogs, while the Acm-protected sulfur enables late-stage functional diversification without perturbing earlier synthetic steps. Selective thiol unveiling supports generation of disulfide-constrained scaffolds, thioether analogs, or sulfur-containing substituents that can modulate lipophilicity and intramolecular interactions. The hydrochloride salt form supports reproducible preparation of protected intermediates used to build libraries of cysteine-containing analogs for structure-function evaluation.

5. Process Chemistry Intermediates

H-D-Cys(Acm)-OH · HCl is suitable for process chemistry intermediate preparation in fine chemical and pharmaceutical intermediate manufacturing where orthogonal protection improves manufacturing robustness. The Acm group provides a chemically stable sulfur protection mode that can withstand common peptide coupling and protection/deprotection sequences, reducing the risk of sulfur oxidation or side-product formation during scale-up. The presence of the α-carboxylic acid and amino functionality supports conversion into activated amino acid derivatives and controlled incorporation into downstream peptide intermediates. Salt handling as the hydrochloride can support consistent material transfer and downstream conversion steps, aligning with industrial workflows that require predictable intermediate behavior for protected amino acid synthesis and subsequent assembly into higher-order products.

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