Fmoc-L-Met-OSu

Fmoc-L-Met-OSu is an Fmoc-protected methionine N-(9H-fluoren-9-ylmethoxycarbonyl) derivative bearing an activated N-hydroxysuccinimide ester (OSu) at the carboxylate position, providing a chiral amino acid framework with stereochemical integrity at the L-configuration. The molecule combines a base-stable, deprotection-ready Fmoc carbamate with a succinimidyl ester that participates in acyl transfer reactions toward nucleophiles such as amines, enabling direct peptide bond formation under peptide-synthesis-compatible conditions. The thioether side chain of methionine remains present as a soft sulfur donor, which can influence coupling selectivity and downstream derivatization chemistry, including oxidation-state dependent transformations. The overall structure functions as a protected amino acid activated ester intermediate, bridging protected amino acid synthesis, peptide coupling chemistry, and bioconjugation-oriented acylation chemistry.

1. Peptide Coupling Chemistry

Fmoc-L-Met-OSu serves as an activated carboxylate for peptide coupling workflows in peptide synthesis and peptide building block preparation, where the OSu ester enables nucleophilic acyl substitution by an amino component. The Fmoc group on the amino nitrogen supports orthogonal protection strategies, allowing stepwise assembly with controlled deprotection and re-coupling cycles. The L-methionine stereocenter is retained during activation and coupling, supporting stereochemically defined peptide analog construction. The thioether side chain can be carried through protected synthesis and later used for selective side-chain functionalization, making the compound suitable for generating methionine-containing sequences and peptide fragments used in structure-activity relationship studies.

2. Bioconjugation Reagents

Fmoc-L-Met-OSu can be applied in chemical biology and biomolecule labeling contexts where NHS ester chemistry is used to form stable amide linkages to lysine-containing proteins, peptide carriers, or amino-functional scaffolds. The activated OSu group reacts readily with primary amines, while the Fmoc carbamate provides a protected handle that can be removed under standard Fmoc deprotection conditions when an amino functionality must be regenerated. The methionine backbone contributes a defined chiral residue and a thioether side chain that may be leveraged for subsequent oxidation or conjugation-state tuning depending on the chosen downstream transformation. Acylation of amine-bearing biomolecules enables preparation of Fmoc-compatible conjugates and peptide-tagged constructs used for analytical research, molecular recognition studies, and reagent generation.

3. Protected Amino Acid Synthesis

Fmoc-L-Met-OSu is suitable for process chemistry intermediate preparation in amino acid derivative manufacturing, where conversion between protected amino acids and activated esters supports scalable coupling-ready feedstock design. The Fmoc-protected amine and OSu-activated carboxyl group provide a controlled functional-group arrangement that can be routed into automated peptide synthesis or into custom coupling steps for fine chemical production. The chiral L-methionine structure ensures that stereochemical specifications are maintained through the activation stage, supporting consistent downstream peptide assembly. The activated ester form also supports streamlined derivatization planning, since the OSu handle can be consumed in coupling or acylation steps to generate amide-containing intermediates for peptide analog libraries.

4. Side-Chain Functionalization

Fmoc-L-Met-OSu supports side-chain functionalization strategies that exploit methionine's thioether chemistry after peptide or conjugate construction. The OSu activation enables incorporation of methionine into amide-linked frameworks, after which the sulfur-containing side chain can be transformed into oxidized sulfoxide or sulfone motifs or used as a handle for further chemical modification depending on the desired molecular property. The presence of the Fmoc protecting group allows orthogonal manipulation of the backbone nitrogen, enabling synthetic sequences where side-chain modifications are performed after coupling while maintaining control over amide stability. Downstream products derived from this intermediate can serve as defined peptidomimetic elements, analytical standards, or functionalized fragments for SAR studies and molecular design campaigns.

5. Pharmaceutical Intermediate Preparation

Fmoc-L-Met-OSu can be employed as a protected amino acid activated ester intermediate for manufacturing of peptide-like building blocks used in pharmaceutical intermediate supply chains and specialty chemical production. The combination of Fmoc protection and OSu activation aligns with common synthetic logic for producing amide-linked fragments with predictable reactivity toward amines, supporting robust coupling steps in fine chemical synthesis. The methionine residue provides a structurally defined, stereochemically consistent component that can be incorporated into peptidomimetic scaffolds or linker motifs for downstream elaboration. The resulting amide-containing intermediates can be further processed into higher-complexity structures used in applied product development and industrial-scale synthesis planning.

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