Fmoc-D-Cys(Acm)-OH

Fmoc-D-Cys(Acm)-OH is a chiral, N-Fmoc-protected cysteine derivative in which the thiol side chain is masked as an Acm thioamide (Acm) group, preserving the stereodefined D-configuration at the α-carbon. The molecule contains a free carboxylic acid for C-terminal activation and an Fmoc carbamate for orthogonal N-protection during solid-phase peptide synthesis. The Acm-protected sulfur is stable under many peptide-coupling conditions yet can be selectively deprotected to regenerate a reactive thiol or to enable disulfide formation strategies. The combination of an Fmoc handle, a latent thiol functionality, and a defined stereocenter makes this compound suitable for cysteine-containing peptide building block preparation and downstream sulfur chemistry.

1. Peptide Synthesis

Fmoc-D-Cys(Acm)-OH is used as a protected cysteine building block for peptide assembly workflows requiring controlled thiol chemistry. The Fmoc group supports stepwise N-terminal deprotection and coupling, while the carboxylic acid participates in standard peptide bond formation to install the residue at a defined position. The Acm-protected side chain tolerates typical coupling and base treatments, enabling incorporation of D-cysteine into peptides without premature sulfur reactivity. Selective Acm removal after chain assembly can generate a free thiol for disulfide exchange, thioether formation, or site-specific conjugation, supporting robust peptide synthesis and cysteine patterning in research-grade sequences.

2. Side-Chain Functionalization

Fmoc-D-Cys(Acm)-OH serves in synthetic organic chemistry as a stereodefined precursor for sulfur-functionalized intermediates and late-stage derivatization. The protected thiol functionality encoded by the Acm group can be unveiled under orthogonal conditions to access nucleophilic thiol chemistry, including alkylation, acylation, or electrophile capture for thioether construction. The D-stereocenter can be leveraged to probe stereochemical effects on binding, stability, or conformational behavior in sulfur-containing scaffolds. The retained carboxylic acid and Fmoc-protected amine also allow conversion into additional protected forms or coupling-ready derivatives, supporting sequential transformations from amino acid chemistry to functional molecular intermediates.

3. Bioconjugation Chemistry

Fmoc-D-Cys(Acm)-OH is applicable to bioconjugation and chemical biology workflows that require cysteine-selective attachment points with stereochemical control. The Acm-protected cysteine side chain can be kept inert during peptide or linker construction, then converted to a thiol for controlled conjugation to maleimides, haloacetamides, or other thiol-reactive handles. The Fmoc-protected nitrogen enables preparation of peptide-based linkers with defined N-terminus chemistry, while the carboxylic acid can support attachment to scaffolds through amide formation. D-cysteine incorporation can be used to tune conjugate stability and resistance to proteolysis, enabling downstream generation of labeled peptides, protein conjugates, or modular biomolecule constructs from a single chiral cysteine precursor.

4. Peptidomimetics And SAR Studies

Fmoc-D-Cys(Acm)-OH supports peptidomimetic construction and structure-activity relationship studies where cysteine stereochemistry and sulfur functionality influence molecular recognition. The Fmoc-protected amine and carboxylic acid enable incorporation into analog libraries through peptide coupling chemistry, while the Acm group provides a protected handle for later sulfur transformations. Thiol regeneration after assembly can facilitate disulfide-constrained analog design or conversion to thioether motifs that modulate conformational restriction. The defined D-configuration at the α-carbon helps generate stereochemically distinct analogs for SAR comparisons, linking amino acid derivatization strategy to measurable changes in scaffold behavior in biochemical research settings.

5. Pharmaceutical Intermediate Preparation

Fmoc-D-Cys(Acm)-OH is suitable for industrial fine chemical synthesis routes that require protected amino acid intermediates for downstream active ingredient related materials. The orthogonal protection pattern, consisting of Fmoc on the amino group and Acm on the thiol side chain, supports manufacturing-compatible handling during intermediate isolation and coupling steps while minimizing side reactions from free sulfur. The free carboxylic acid enables conversion into activated derivatives for controlled incorporation into larger fragments, including peptide-like intermediates and sulfur-containing linkers. Acm deprotection and subsequent thiol-based transformations can be integrated as a downstream step to furnish thiol or disulfide motifs used in process chemistry intermediate preparation for specialized chemical manufacturing programs.

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