Ac-Cys-OMe)2 contains a cysteine-derived amino acid motif in which the amino group is acetylated (Ac) and the carboxyl functionality is present as a methyl ester (OMe), with the overall structure corresponding to a protected amino acid derivative rather than a free amino acid. The cysteine side chain bears a thiol (-SH) functionality that can participate in thiol-disulfide chemistry or be used as a nucleophilic handle for further derivatization, while the acetylated amino and esterified carboxyl groups reduce free amine and carboxyl reactivity. As a stepwise peptide-chemistry intermediate or building block, the protected Cys methyl ester form is employed in synthesis workflows and chemical labeling strategies where controlled handling of the thiol and protected termini are required.
CAT No: CP26998
CAS No:32381-28-5
Synonyms/Alias:N-Acetyl-L-cysteinemethylester;7652-46-2;L-Cysteine,N-acetyl-,methylester;methyl(2R)-2-acetamido-3-sulfanylpropanoate;ZINC04521105;(Ac-Cys-OMe)2;SCHEMBL112332;AC1O724C;01042_FLUKA;CTK5E3058;MolPort-003-925-126;QTKAQJWFVXPIFV-YFKPBYRVSA-N;ZINC4521105;MFCD00237476;L-Cysteine,N-acetyl-,methylester;N-ACETYL-L-CYSTEINEMETHYLESTER;AKOS015906923;VZ33067;AM013328;SC-68287;(R)-methyl2-acetamido-3-mercaptopropanoate;FT-0655063;methyl(2R)-2-acetamido-3-sulfanyl-propanoate;A838735;(2R)-2-acetamido-3-mercaptopropanoicacidmethylester
(Ac-Cys-OMe)2 is a thioether-containing cysteine derivative presented as an amino-acid methyl ester with N-acetyl protection, where the cysteine side chain remains available for chemical handling while the amino functionality is masked to support controlled reactivity in downstream steps. This protected, esterified format is commonly used as a stable building block in peptide-related synthesis and as an intermediate for preparing cysteine-containing motifs without introducing free amine or carboxyl groups that would otherwise complicate coupling or purification. The presence of the thioether sulfur makes it particularly relevant for constructing cysteine-derived structures and for workflows where sulfur-containing functional groups must be introduced in a protected, manageable form.
1. Cysteine Motif Building
(Ac-Cys-OMe)2 is used by peptide and peptidomimetic developers to assemble cysteine-containing fragments where the amino group is acetyl-protected and the carboxyl group is present as a methyl ester, helping maintain chemoselectivity during segment preparation. Research groups building sulfur-containing linkages and cysteine-bearing side-chain patterns often select this type of protected cysteine derivative to reduce side reactions that can occur with free amino or carboxyl functionalities. In custom peptide synthesis and medicinal chemistry intermediate development, the thioether sulfur provides a handle for subsequent functionalization steps that install or elaborate sulfur chemistry on the growing scaffold.
2. Pharmaceutical Intermediate Synthesis
(Ac-Cys-OMe)2 is frequently incorporated into pharmaceutical intermediate workflows that require a cysteine-derived building block with controlled functional-group reactivity and simplified purification profiles. Process development teams and specialty chemical manufacturers use protected cysteine esters to generate defined sulfur-containing intermediates for further elaboration into larger fragments, including side-chain-modified amino acid derivatives used in lead optimization chemistry. The acetylated amino and esterified carboxyl pattern supports downstream transformations on the sulfur functionality while minimizing competing reactions from unprotected polar groups.
3. Thioether Functionalization Studies
(Ac-Cys-OMe)2 supports chemical biology and medicinal chemistry programs that explore sulfur chemistry on cysteine-derived scaffolds, including the preparation of defined thioether-containing intermediates for structure-activity relationship studies. Chemical research groups often choose this derivative when they need a sulfur-bearing amino acid unit in a protected format that is stable enough for multi-step synthesis and handling. The methyl ester and N-acetyl protection help keep the molecule focused on sulfur-centered derivatization, enabling controlled generation of downstream cysteine-like motifs used in probe, ligand, or scaffold construction workflows.
4. Analytical Reference Material Development
(Ac-Cys-OMe)2 is also used in analytical method development and reference preparation for workflows that require cysteine-derived standards with a defined protection pattern and sulfur-containing side chain. In LC-MS and related characterization pipelines, laboratories may use this compound to validate retention behavior, confirm derivatization outcomes, or support identification of cysteine-derivative intermediates generated during synthetic campaigns. The fixed N-acetyl and methyl ester functional-group pattern provides a consistent chemical signature that can be advantageous when monitoring multi-step transformations involving sulfur-containing amino acid derivatives.
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