Fmoc-Met-OPfp

Fmoc-Met-OPfp is an N-Fmoc protected methionine derivative bearing an activated pentafluorophenyl ester (OPfp) at the carboxyl group, combining a stable peptide-synthesis handle with a highly reactive acyl leaving group. The molecule contains an α-amino acid stereocenter in the methionine backbone, an Fmoc carbamate for orthogonal N-protection during stepwise coupling, and a thioether side chain that can participate in oxidation-state-dependent chemistry without requiring additional protection in many peptide workflows. The OPfp ester is designed to undergo acyl transfer under peptide coupling conditions, enabling conversion to amide linkages with nucleophiles such as amino groups while maintaining compatibility with Fmoc-based strategies. The presence of the fluorinated aromatic ester also supports downstream analytical detectability and can serve as a controlled intermediate in amino acid ester and activated-acid chemistry.

1. Peptide Synthesis

Fmoc-Met-OPfp is applied in Fmoc solid-phase and solution-phase peptide synthesis where an activated C-terminal methionine unit is required for efficient peptide bond formation. The OPfp ester provides a strong acyl-transfer driving force toward amine nucleophiles, while the Fmoc group maintains the methionine nitrogen in a protected, coupling-compatible state. The thioether side chain of methionine remains chemically defined during coupling steps, supporting incorporation into peptides that later undergo oxidation or side-chain functionalization as needed. The resulting methionine amide products can be extended further by standard Fmoc deprotection and subsequent coupling cycles, making the compound a practical intermediate for peptide building block preparation.

2. Side-Chain Functionalization

Fmoc-Met-OPfp supports chemical biology and peptide engineering workflows that require methionine side-chain modification after incorporation into a peptide scaffold. The methionine thioether can be selectively transformed through controlled oxidation-reduction sequences to access sulfoxide or sulfone-containing derivatives, while the OPfp activation and Fmoc protection enable reliable assembly of the precursor peptide or amide. The fluorinated OPfp leaving group facilitates formation of the initial amide linkage, after which side-chain chemistry can be addressed under conditions tailored to sulfur oxidation state. Downstream derivatives produced from the methionine-containing peptide can serve as probes for oxidation-sensitive behavior, protein stability studies, or peptidomimetic design where sulfur oxidation state is a structural parameter.

3. Chiral Amino Acid Intermediate

Fmoc-Met-OPfp functions as a chiral methionine-based intermediate for stereochemically controlled synthesis of amino acid derivatives and peptide analogs. The stereogenic center retained in the methionine backbone enables transfer of the correct configuration into coupled amide products, which is critical for structure-activity relationship studies and for building stereochemically consistent peptide libraries. The orthogonal combination of Fmoc N-protection and OPfp C-activation allows sequential manipulation of functional groups: N-deprotection can be triggered independently from acyl transfer events, supporting controlled intermediate generation. Use of this chiral activated amino acid can streamline downstream preparation of protected amino acids, activated esters, and amide-linked intermediates for fine chemical synthesis and stereochemical SAR campaigns.

4. Bioconjugation Chemistry

Fmoc-Met-OPfp can be employed in bioconjugation and chemical protein modification strategies that require methionine-derived amide formation under controlled coupling conditions. The OPfp ester enables acylation of primary amines present on biomolecule linkers, peptides, or engineered protein tags, while the Fmoc group can be managed to match the compatibility window of the conjugation sequence. The methionine residue embedded in the conjugate provides a chemically recognizable motif that may participate in subsequent oxidation-state-dependent behavior, which can be relevant for conjugate stability and labeling schemes. The resulting methionine-containing conjugates can serve as intermediates for generating labeled biomolecules, affinity reagents, or functionalized peptide conjugates used in biochemical research.

5. Pharmaceutical Intermediate Preparation

Fmoc-Met-OPfp is suitable for pharmaceutical intermediate preparation where methionine-containing building blocks are required for peptidic or peptidomimetic chemistries. The activated OPfp carboxyl group supports formation of amide linkages that can be carried into larger synthetic sequences, while the Fmoc-protected amine provides a controlled protection strategy aligned with common peptide-manufacturing workflows. The thioether side chain can be treated as a defined sulfur functionality during route design, enabling later conversion to oxidized forms or incorporation into stability-tuned analogs. Downstream synthesis can leverage the compound as a process-compatible intermediate for generating protected methionine units, activated acid derivatives, and amide-linked intermediates used in specialty chemical production.

6. Analytical Research Standards

Fmoc-Met-OPfp can be used as an analytical reference and method-development intermediate for monitoring Fmoc-based peptide coupling chemistry and activated ester behavior. The combination of Fmoc chromophore and fluorinated OPfp group provides strong spectroscopic and mass spectrometric signatures that can aid in tracking conversion, identifying activated-acid species, and verifying intermediate integrity during synthesis. The defined methionine stereochemistry and thioether functionality support consistent analytical comparisons across synthesis runs and derivative formation steps. Analytical workflows that quantify coupling efficiency, impurity profiles, or intermediate consumption can incorporate this compound to support characterization of peptide building block preparation and activated-acid handling in applied amino acid chemistry.

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