Boc-Cys(Z-aminoethyl)-OH is a protected cysteine derivative in which the amino group is masked with a Boc (tert-butoxycarbonyl) protecting group and the thiol functionality is converted into a thioether via a Z-aminoethyl substituent. The molecule contains a free carboxylic acid and a side-chain thioether bearing an aminoethyl terminus, providing both a protected cysteine backbone and a latent primary amine for further coupling or derivatization, while the Z substituent denotes the specific protecting/functional group arrangement on the cysteine side chain. As a stepwise peptide-synthesis building block and chemical biology intermediate, it supports controlled chemoselectivity by keeping the backbone nitrogen protected and enabling selective functionalization of the side-chain amino handle for conjugation, labeling, or preparation of more complex amino acid and peptide derivatives.
CAT No: CP27523
CAS No:85003-76-5
Synonyms/Alias:BOC-CYS(Z-AMINOETHYL)-OH;85003-76-5;AC1OLR9K;Boc-L-4-thialysine(Z)-OH;SCHEMBL1429551;WOISIWBKIILOSH-AWEZNQCLSA-N;ZINC4899646;6297AH;KM2276;N-t-Butoxycarbonyl-S-(2-carbobenzyloxyaminoethyl)-L-cysteine;N-(tert-Butoxycarbonyl)-S-[2-(benzyloxycarbonylamino)ethyl]-L-cysteine;(R)-3-(2-benzyloxycarbonylaminoethylsulfanyl)-2-tert-butoxycarbonylaminopropionicacid;(2R)-2-[(2-methylpropan-2-yl)oxycarbonylamino]-3-[2-(phenylmethoxycarbonylamino)ethylsulfanyl]propanoicacid
Boc-Cys(Z-aminoethyl)-OH is a Boc-protected cysteine derivative bearing a side-chain Z-aminoethyl substituent, providing an amino-functionalized handle while maintaining the cysteine thiol chemistry masked for controlled downstream use. This protected amino acid building block is commonly selected for peptide and peptidomimetic assembly workflows where cysteine functionality must be handled with orthogonal protection and where an additional amino group is required for later derivatization. The Z-aminoethyl side chain also supports applications that benefit from increased polarity and the ability to introduce further functional groups after peptide coupling.
1. Peptide Building Block
Boc-Cys(Z-aminoethyl)-OH is used as a protected cysteine building block in custom peptide synthesis, particularly when the target sequence requires a cysteine residue equipped with a side-chain aminoethyl functionality. Peptide synthesis teams choose this reagent to ensure the cysteine backbone is compatible with standard protected-amino-acid coupling strategies while retaining a functional side-chain amine for downstream modification of the assembled peptide. This approach is frequently applied in the preparation of peptide libraries, segment-based synthesis, and the generation of peptide analogs where side-chain functionalization is planned after assembly rather than during the coupling sequence.
2. Peptidomimetic Side-Chain Functionalization
Boc-Cys(Z-aminoethyl)-OH supports peptidomimetic development where an aminoethyl group on the cysteine side chain is leveraged as a derivatization site to tune physicochemical properties or to attach additional moieties. Medicinal chemistry and chemical biology groups use this building block to prepare analog series that require controlled introduction of amine-reactive handles, enabling subsequent conjugation steps such as acylation, reductive amination, or formation of amide-linked substituents on the side chain. By incorporating the aminoethyl functionality at the building-block stage, researchers can maintain structural consistency across analogs while deferring the final functional-group installation to later stages.
3. Bioconjugation Handle Introduction
Boc-Cys(Z-aminoethyl)-OH is frequently incorporated into peptides intended for bioconjugation workflows because the Z-aminoethyl side chain provides a primary amine that can serve as a practical attachment point after peptide assembly. Chemical biology groups use this reagent to generate conjugation-ready peptide scaffolds for linking to polymers, linkers, or other biomolecular partners using amine-selective coupling chemistries. In these workflows, the Boc protection on the amino terminus and the protected cysteine functionality help ensure that the conjugation chemistry is directed to the intended amine handle rather than causing uncontrolled side reactions during peptide synthesis and purification.
4. Pharmaceutical Intermediate Development
Boc-Cys(Z-aminoethyl)-OH is also used as a pharmaceutical intermediate building block when a protected cysteine motif with an aminoethyl side chain is required for constructing larger, functionalized molecules. Process development and medicinal chemistry teams select this compound to introduce a defined, protected amino acid fragment that can be carried through multi-step synthesis toward amine-containing intermediates used in SAR studies and final candidate synthesis. The combination of a protected amino terminus and a side-chain aminoethyl group supports modular assembly strategies, where the amino functionality is preserved for later transformation while the protected framework maintains compatibility with stepwise synthetic operations.
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