H-D-Cys(Bzl)-OH is a protected, deuterated cysteine derivative in which the amino acid core bears a benzylthio-protected side chain (Cys(Bzl)) and an N-terminal deuterium label (H-D) while retaining the carboxylic acid functionality. The molecule contains both an amino group and a carboxylic acid group, with the thiol functionality masked as a benzyl thioether to control chemoselectivity during peptide-related transformations. It is used as a building block for preparing cysteine-containing peptides and for chemical labeling or structural studies where a protected cysteine side chain and isotopic substitution are required to support controlled coupling and analytical discrimination.
H-D-Cys(Bzl)-OH is a stereodefined cysteine derivative in which the amino acid backbone is presented as a free carboxylic acid and an N-terminal deuterated amine (H-D), while the thiol side chain is protected as a benzyl thioether (Cys(Bzl)). The molecule contains a single chiral center at the cysteine alpha position, and the benzyl-protected sulfur provides a stable thioether handle that can be selectively transformed to thiol-containing species under appropriate conditions. The deuterium label at the amino group enables isotopically tracked behavior in peptide coupling, side-chain modifications, and analytical workflows, while the carboxylic acid supports standard amino acid activation chemistry. Overall, H-D-Cys(Bzl)-OH functions as a chiral, protected amino acid intermediate compatible with peptide building block preparation and downstream sulfur-functionalization chemistry.
1. Peptide Synthesis
H-D-Cys(Bzl)-OH is applied in peptide synthesis workflows where cysteine residues require controlled sulfur chemistry during chain assembly. The protected thioether (Bzl) suppresses undesired thiol oxidation and side reactions during coupling, while the free carboxylic acid and deuterated amino functionality enable incorporation as a cysteine-equivalent building block under peptide coupling conditions. The stereodefined cysteine center supports stereochemically consistent peptide analog construction, and the N-deuterium label can be retained for mechanistic studies or mass spectrometric traceability. The resulting peptide products can be further processed to generate thiol-bearing peptides, thioether-to-thiol conversions, or disulfide-forming intermediates after deprotection.
2. Chemical Biology Labeling
H-D-Cys(Bzl)-OH is suitable for chemical biology and proteomics-adjacent labeling strategies that benefit from isotopic discrimination at the cysteine nitrogen environment. The deuterium at the amino group can be used as a stable isotope marker for tracking incorporation events, monitoring exchange processes, or distinguishing labeled peptide fragments in LC-MS/MS workflows. The benzyl thioether protection enables handling under conditions that might otherwise oxidize free cysteine thiols, supporting controlled preparation of cysteine-containing probes or peptide substrates. Downstream conversion to thiol-reactive forms can enable conjugation chemistries targeting thiol-specific electrophiles, supporting amino acid chemistry-driven biomolecule modification.
3. Peptidomimetic Construction
H-D-Cys(Bzl)-OH is employed in peptidomimetic and constrained scaffold synthesis where cysteine-derived sulfur functionality must be introduced with controlled reactivity. The benzyl-protected sulfur participates as a protected side-chain group that can be carried through fragment assembly and then unveiled to generate thiol, thioester, or other sulfur oxidation-state variants depending on the synthetic sequence. The chiral alpha-carbon supports stereochemically defined incorporation into peptide-like backbones, while the deuterated amine can help differentiate analogs during SAR studies by enabling isotopic readouts. The carboxylic acid functionality supports conversion to activated derivatives for coupling into larger peptidomimetic frameworks, linking amino acid derivatization to synthetic methodology development.
4. Process Chemistry Intermediate
H-D-Cys(Bzl)-OH is relevant to process chemistry intermediate preparation for manufacturing routes that require protected cysteine handling with robust storage and predictable coupling behavior. The benzyl thioether protection provides a chemically stable sulfur protecting-group strategy that can reduce variability from thiol oxidation during scale-up operations and intermediate transfers. The free carboxylic acid enables standardized activation and coupling logic in peptide building block production, while the stereochemical integrity of the cysteine center supports consistent downstream product specifications. The deuterium label can be leveraged in isotope-aware process development and analytical release strategies for labeled intermediates and controlled product characterization.
5. Analytical Research Standards
H-D-Cys(Bzl)-OH is used to prepare labeled analytical standards and reference materials for method development in amino acid and peptide quantification. The N-deuterium label provides a distinct mass signature that can improve selectivity in targeted LC-MS/MS assays and support calibration strategies for isotopically resolved analyte species. The benzyl-protected thiol reduces side reactions during sample preparation, enabling reproducible derivatization or controlled conversion to thiol-containing forms when standards require sulfur-reactive endpoints. The compound's compatibility with peptide coupling chemistry also enables generation of cysteine-containing reference peptides for validating chromatographic separation, fragmentation patterns, and isotopic incorporation accuracy in analytical research workflows.
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