(H-Cys-OMe)2 · 2 HCl

(H-Cys-OMe)2 · 2 HCl is a cysteine methyl ester hydrochloride salt form supplied as a bis-cysteine methyl ester species, providing a protected thiol-containing amino acid building block for downstream thiol chemistry and peptide-related derivatization workflows. The presence of amino ester functionalities and the cysteine side-chain sulfhydryl group make it a practical reagent for preparing cysteine-containing intermediates, thioether/thioester derivatives, and thiol-reactive materials under controlled conditions, while the hydrochloride salt form supports handling and salt-stabilized storage.

1. Thiol-Functional Intermediate Synthesis

(H-Cys-OMe)2 · 2 HCl is used by medicinal chemistry and peptide-intermediate development groups to build cysteine-containing fragments where the thiol side chain needs to be carried through as a reactive handle for subsequent conversion to thioethers, thioesters, or disulfide-linked motifs. Its amino acid ester form is commonly selected when downstream steps require a defined, ester-based functionality rather than a free carboxylate, enabling straightforward coupling into larger synthetic sequences or preparation of cysteine-rich intermediates for custom peptide manufacturing.

2. Cysteine-Containing Peptide Building Blocks

(H-Cys-OMe)2 · 2 HCl supports workflows that require cysteine methyl ester functionality for assembling peptide segments or generating cysteine-containing derivatives prior to final deprotection and activation steps. Research groups performing solution-phase peptide synthesis and intermediate screening often choose this type of cysteine ester salt when they need a stable, isolable cysteine unit that can be carried into segment condensation strategies, particularly for constructs where thiol chemistry will be managed in later steps to control side reactions.

3. Bioconjugation Linker Preparation

(H-Cys-OMe)2 · 2 HCl is applied in chemical biology and bioconjugation development to prepare cysteine-derived linkers and thiol-reactive intermediates used for protein and peptide modification strategies. The cysteine sulfhydryl functionality provides a direct entry point to thiol-based conjugation chemistries, while the ester form helps define the carboxyl-side functionality of the linker prior to coupling to biomolecules or surfaces, supporting consistent reagent design for labeling, immobilization, and conjugate library generation.

4. Biomaterials Crosslinking Precursors

(H-Cys-OMe)2 · 2 HCl is used in biomaterials science as a cysteine-based precursor for thiol-directed crosslinking and surface functionalization routes, where controlled thiol availability is required to form stable thioether or disulfide-linked networks. Materials researchers often select this reagent form to introduce cysteine motifs into polymer or hydrogel formulations, enabling tunable crosslinking density and facilitating downstream processing steps that rely on thiol reactivity while maintaining a defined ester functionality during formulation development.

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