(H-D-Cys-OMe)2 · 2 HCl

(H-D-Cys-OMe)2 · 2 HCl is a cysteine-derived, methyl ester material supplied as a dipeptide-like dimeric form in the presence of hydrochloride salts, providing a protected carboxyl functionality (methyl ester) while retaining the thiol-bearing cysteine chemistry in a form commonly handled under acidic conditions. The stereochemical designation and esterified carboxyl group make it a practical building block for downstream transformations where cysteine reactivity needs to be controlled, particularly in peptide and sulfur-containing motif synthesis. Researchers also use this salt form when they require a defined cysteine equivalent with improved handling relative to free thiol acids.

1. Sulfur-Containing Motif Synthesis

(H-D-Cys-OMe)2 · 2 HCl is used by synthetic organic and peptide chemistry groups to build sulfur-containing fragments where cysteine functionality is required as a controlled intermediate. The methyl ester carboxyl form supports coupling or conversion into activated derivatives during the preparation of thioether- or thioamide-containing intermediates, while the hydrochloride salt form helps maintain consistent handling in multistep workflows. This product is frequently selected in laboratory programs that require a cysteine equivalent with a defined functional-group pattern rather than starting from free cysteine salts.

2. Peptide Fragment Building Block

(H-D-Cys-OMe)2 · 2 HCl supports the assembly of cysteine-containing peptide fragments and modified peptide segments in custom peptide synthesis and medicinal chemistry research. The esterified carboxyl group is particularly useful when preparing intermediate segments that need further functional conversion prior to final coupling into a larger sequence. Because cysteine residues are central to disulfide topology and sulfur chemistry in peptides, this reagent is commonly used when a cysteine-containing building block must be introduced in a controlled manner compatible with subsequent peptide-manufacturing steps.

3. Thiofunctional Intermediate Development

(H-D-Cys-OMe)2 · 2 HCl is applied in the development of thiofunctional intermediates for medicinal chemistry and specialty chemical manufacturing, including routes that convert cysteine-derived thiol chemistry into thioethers or other sulfur-containing substituents. The defined cysteine-derived scaffold and ester-protected carboxyl functionality make it useful for preparing intermediates that can be carried forward into heterocycle formation, late-stage functionalization, or side-chain diversification. Teams working on sulfur-rich small molecules often choose this reagent to streamline procurement of a cysteine equivalent with established downstream reactivity.

4. Analytical Reference Material Preparation

(H-D-Cys-OMe)2 · 2 HCl is used in analytical method development and reference preparation where cysteine-derived standards or calibration components are needed for monitoring sulfur-containing species and related derivatization workflows. In LC-based or derivatization-assisted analytical studies, having a defined cysteine-containing esterified scaffold can improve reproducibility when comparing response across batches or validating sample preparation steps. Analytical groups also rely on such defined cysteine equivalents to support method transfer and troubleshooting for assays that involve sulfur-functional handling.

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