Fmoc-D-Cys(Trt)-OPfp

Fmoc-D-Cys(Trt)-OPfp is an Fmoc-protected D-cysteine derivative bearing a Trt-protected thiol side chain and an OPfp ester at the carboxyl terminus, forming a chiral amino acid building block designed for controlled peptide coupling. The molecule contains a stereogenic center at the D-configuration alpha-carbon, an Fmoc carbamate for temporary N-protection during stepwise synthesis, and a thioether-masked cysteine side chain stabilized by the Trt group to suppress thiol reactivity and disulfide scrambling. The OPfp leaving group on the activated carboxylate enables acyl transfer under peptide coupling conditions while maintaining compatibility with orthogonal protection strategies. The combined protection pattern yields a chemically addressable cysteine handle upon deprotection, supporting downstream formation of thiol-containing peptides, thioether/thiol modifications, and thioamide or disulfide-linked derivatives.

1. Peptide Synthesis

Fmoc-D-Cys(Trt)-OPfp is used in peptide synthesis workflows where a D-configured cysteine residue with a protected thiol is required for stereochemically defined sequence assembly. The Fmoc carbamate supports standard N-terminal deprotection and subsequent coupling, while the Trt-thio protection maintains sulfur inertness during chain elongation and minimizes side reactions such as thioester or disulfide formation. The OPfp ester at the C-terminus functions as an activated carboxyl component that can participate in peptide bond formation to install the cysteine residue with controlled acyl transfer. The resulting D-cysteine-containing peptides can be carried forward to thiol-unmasked analogs for further functionalization, cyclization, or disulfide engineering, aligning with peptide science and synthetic methodology needs.

2. Side-Chain Functionalization

Fmoc-D-Cys(Trt)-OPfp is applicable to side-chain functionalization strategies that target cysteine chemistry after orthogonal deprotection. The Trt-protected thiol can be selectively unmasked to generate a reactive thiol for subsequent conjugation, alkylation, acylation, or disulfide bond formation, enabling access to thiol-bearing peptide fragments and cysteine-based functional motifs. The D-stereochemistry can be leveraged to tune conformational preferences and protease stability in peptide analogs used for chemical biology and structure-activity relationship studies. The OPfp-activated carboxyl and Fmoc-protected amine arrangement also supports incorporation into larger constructs before installing sulfur-specific modifications, supporting a clear synthetic sequence from protected building block to functionalized product.

3. Chemical Biology Probes

Fmoc-D-Cys(Trt)-OPfp serves as a chiral building block for chemical biology probe construction where cysteine side chains are used as handles for labeling and target engagement studies. The protected thiol and Fmoc group allow stepwise assembly of peptide scaffolds that retain sulfur reactivity in reserve until deprotection, supporting controlled introduction of thiol-reactive moieties such as maleimide, iodoacetamide, or disulfide-forming partners. The D-configuration can be incorporated to generate stereochemically defined probes that may exhibit altered binding modes or reduced susceptibility to proteolysis compared with L analogs, which is relevant for probe stability and interpretability in biochemical assays. The amino acid derivative nature of Fmoc-D-Cys(Trt)-OPfp also supports downstream generation of labeled fragments, immobilizable linkers, and modular probe libraries for biochemical research.

4. Bioconjugation Chemistry

Fmoc-D-Cys(Trt)-OPfp is suitable for bioconjugation chemistry that relies on cysteine-directed coupling to biomolecules or biomolecule-derived materials. The Trt-protected thiol enables preparation of cysteine-bearing peptide intermediates that can be deprotected to expose a thiol for conjugation under thiol-selective conditions, supporting formation of thioether linkages or disulfide-linked conjugates. The Fmoc-protected amine and OPfp-activated carboxyl functionality allow efficient incorporation into peptide carriers, affinity tags, or multivalent scaffolds prior to conjugation, aligning with modular manufacturing of conjugation-ready intermediates. The stereodefined D-cysteine residue can contribute to conjugate stability and structural control, supporting reproducible generation of conjugates used in applied biochemical research and specialty chemical production.

5. Pharmaceutical Intermediate Preparation

Fmoc-D-Cys(Trt)-OPfp can be employed as a process-relevant intermediate for manufacturing peptide-based active ingredients, peptide intermediates, or peptide-like building blocks used in pharmaceutical development. The orthogonal protection scheme, consisting of Fmoc for N-protection and Trt for thiol masking, supports predictable deprotection and minimizes undesired sulfur chemistry during synthesis and purification, which is important for scalable peptide construction. The OPfp ester activation at the carboxyl terminus provides a coupling-ready form that can be integrated into controlled synthetic routes for producing D-cysteine-containing sequences. The resulting protected peptide fragments and cysteine-unmasked derivatives can serve as downstream inputs for formulation-grade materials, analytical standards, or further derivatization steps in fine chemical synthesis and pharmaceutical intermediate preparation.

6. Process Chemistry Intermediate

Fmoc-D-Cys(Trt)-OPfp is used in process chemistry contexts where activated amino acid derivatives and orthogonal protecting groups are required to manage reactivity and improve synthetic control. The OPfp ester functionality can support acylation steps that are compatible with established peptide coupling paradigms, while the Fmoc and Trt groups provide operational stability by suppressing free amine and thiol reactivity during intermediate handling. The defined D-stereocenter ensures stereochemical fidelity across manufacturing batches when producing D-cysteine-containing peptide intermediates and peptidomimetic fragments. The compound's design as a protected amino acid derivative supports downstream deprotection to generate thiol-reactive intermediates for sulfur-specific transformations, enabling robust translation from synthetic methodology to industrial chemical manufacturing of amino acid-derived building blocks.

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