Fmoc-Cys(2-hydroxyethyl)-OH

Fmoc-Cys(2-hydroxyethyl)-OH is an Fmoc-protected cysteine derivative bearing a side-chain 2-hydroxyethyl substituent, giving a chiral amino acid framework with a thioether-compatible cysteine scaffold. The molecule contains an Fmoc carbamate for orthogonal N-protection, a free carboxylic acid for C-terminal peptide coupling, and a side-chain hydroxyl group that can participate in hydrogen bonding and can be further functionalized under standard organic transformations. The thioether-bearing cysteine topology provides a sulfur-containing handle that can influence reactivity in peptide assembly and downstream derivatization, while the stereogenic center supports stereodefined incorporation into peptide sequences and chiral intermediate synthesis. The presence of both protected and reactive functional groups makes it suitable for stepwise protected amino acid synthesis and for generating defined amino acid building blocks for peptide and bioconjugation workflows.

1. Peptide Synthesis

Fmoc-Cys(2-hydroxyethyl)-OH is used in peptide synthesis as an Fmoc-protected cysteine-based building block for solid-phase or solution-phase coupling, where the Fmoc group enables controlled N-deprotection and iterative chain elongation. The free carboxylic acid supports amide bond formation at the C-terminus, while the side-chain 2-hydroxyethyl hydroxyl enables orthogonal chemoselective modifications after peptide assembly. The chiral cysteine backbone stereochemistry allows incorporation of a defined configuration into peptide sequences, supporting reproducible structure-function studies and sequence-dependent reactivity. The resulting hydroxyl-functional thioether-containing residue can be carried through to generate peptide analogs with tailored polarity, solubility, and conjugation potential for downstream synthetic and analytical needs in amino acid chemistry.

2. Bioconjugation Chemistry

Fmoc-Cys(2-hydroxyethyl)-OH is applied to bioconjugation workflows requiring amino acid-derived handles for controlled attachment of biomolecules, where the side-chain hydroxyl can serve as a functional group for linker elaboration and conjugate tuning. The Fmoc-protected amine and carboxylic acid support preparation of peptide-based conjugation reagents, including short cysteine-containing motifs that can be assembled into targeting or scaffold peptides. The sulfur-containing cysteine-derived motif can be leveraged in synthetic strategies that depend on sulfur chemistry while maintaining the hydroxyl-bearing side chain for hydrogen-bonding interactions and improved conjugate solubility. The stereodefined amino acid residue helps maintain consistent three-dimensional presentation of the conjugation site in chemical biology and applied biomolecule modification.

3. Peptidomimetics And SAR Studies

Fmoc-Cys(2-hydroxyethyl)-OH is suitable for peptidomimetic construction and structure-activity relationship studies because the residue combines a protected amino acid backbone with a side-chain hydroxyl that can modulate polarity and local conformational preferences. The Fmoc group supports systematic incorporation into peptide analogs, while the free carboxyl functionality enables coupling to amines or activated derivatives to build defined amide-linked scaffolds for SAR campaigns. The chiral center in the cysteine framework enables stereochemical control when mapping how stereochemistry and side-chain functionalization affect binding or stability in screening libraries. The hydroxyl-bearing 2-hydroxyethyl substituent can be transformed into alternative functional groups to generate analog series that probe the role of hydrogen-bonding and linker length in amino acid derivative design.

4. Protected Amino Acid Derivatization

Fmoc-Cys(2-hydroxyethyl)-OH is used as a protected amino acid intermediate for side-chain functionalization strategies where the orthogonal Fmoc protection allows selective manipulation of the carboxyl group and side-chain hydroxyl chemistry at different stages. The Fmoc carbamate enables controlled N-deprotection for peptide coupling, while the side-chain hydroxyl can be protected, activated, or converted to ether/ester derivatives to tune reactivity and solubility during multistep synthesis. The cysteine-derived sulfur-containing framework provides a chemically distinct functional element that can be carried through as a stable thioether motif or used as a handle in later derivatization sequences. The defined stereochemistry supports reproducible formation of chiral intermediates for fine chemical synthesis, including downstream protected amino acid synthesis and chiral building block preparation for complex molecular targets.

5. Pharmaceutical Intermediate Preparation

Fmoc-Cys(2-hydroxyethyl)-OH is relevant to pharmaceutical intermediate preparation where amino acid-derived fragments are assembled into peptide-like or peptidomimetic structures for process chemistry and medicinal chemistry programs. The Fmoc-protected amine and carboxylic acid enable standardized coupling logic for generating defined intermediates under peptide synthesis conditions, supporting reproducible batch-to-batch construction of chiral scaffolds. The side-chain 2-hydroxyethyl hydroxyl provides a handle for adjusting hydrophilicity and for enabling controlled downstream transformations that can be aligned with manufacturing route design. The compound's protected amino acid form supports scalable intermediate generation for specialty chemical production and applied synthesis of stereodefined building blocks used in broader chemical manufacturing contexts.

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