FA-Met-OH is a methionine-derived amino acid derivative featuring a free amino acid carboxylic acid (-COOH) and an amino group (-NH2) on the methionine backbone, with an N-substituted "FA" functionality attached to the amino terminus. The molecule retains methionine's thioether-containing side chain, while the "FA" substitution modifies the amino group's reactivity and can influence solubility and subsequent coupling behavior relative to unmodified methionine. FA-Met-OH is used as a building block or intermediate in peptide and amino acid derivative synthesis, including contexts where an amino-terminus functional handle is required for controlled assembly, labeling, or preparation of further protected or conjugated methionine-containing structures.
FA-Met-OH is a formylated methionine derivative in which the amino acid backbone retains the stereogenic center of L-methionine while the α-amino functionality is converted to an N-formyl (formamido) group. The structure presents a free carboxylic acid (OH-bearing C-terminus) alongside a thioether side chain characteristic of methionine, enabling controlled reactivity under peptide-coupling and sulfur-tolerant synthetic conditions. The N-formyl group provides an amide-stabilized nitrogen that can be carried through coupling steps and later removed or transformed depending on the chosen deprotection chemistry. The combination of chiral amino acid configuration, carboxylic acid handle, and sulfur-containing side chain makes FA-Met-OH a practical chiral intermediate and peptide-building precursor for downstream amino acid derivatization and sulfur-functional modifications.
1. Protected Amino Acid Chemistry
FA-Met-OH is used in protected amino acid synthesis workflows where the N-formyl group functions as an amide-protecting strategy for the α-amino nitrogen while maintaining a free carboxylic acid for activation and coupling. The preserved L-configuration supports stereodefined peptide bond formation, and the thioether side chain can be retained during peptide assembly or selectively modified afterward. Carboxylic acid reactivity enables conversion to activated esters or coupling partners under standard peptide coupling conditions, while the formamido nitrogen can be managed through compatible deprotection or transformation steps to reach the desired terminal functionality. FA-Met-OH therefore serves as a chiral intermediate for constructing peptide building blocks and for preparing methionine-containing derivatives with controlled protection-state requirements.
2. Peptide Synthesis
FA-Met-OH is applicable to peptide synthesis and fragment coupling strategies targeting methionine incorporation at defined positions within peptide sequences. The free C-terminal carboxylic acid enables peptide coupling chemistry, while the N-formyl group provides a stable nitrogen state that can be carried through iterative assembly toward longer chains or used as a handle for orthogonal functional group management. The thioether side chain of the methionine residue supports sulfur-tolerant synthetic routes and can be leveraged for subsequent oxidation, alkylation, or thioether-to-sulfoxide/sulfone transformations when sulfur oxidation state is part of the design. FA-Met-OH can be employed to generate methionine-containing peptide analogs and to support stereochemically consistent peptide construction in both research-grade synthesis and controlled manufacturing of peptide intermediates.
3. Side-Chain Functionalization
FA-Met-OH is suitable for side-chain functionalization programs in chemical biology and synthetic organic chemistry that require a methionine sulfur motif with defined stereochemical context. The thioether present in the methionine side chain can undergo controlled oxidation to sulfoxide or further oxidation to sulfone derivatives, enabling modulation of polarity, hydrogen-bond acceptor properties, and conformational preferences in downstream molecules. The formamido-protected nitrogen and free carboxyl group allow sequential functional group transformations, where sulfur modification can be performed while the amino acid backbone remains compatible with subsequent coupling or derivatization. FA-Met-OH thereby supports generation of sulfur-state variants used in peptide analog libraries, mechanistic probes, and intermediate preparation for functionalized amino acid derivatives.
4. Chemical Biology Probes
FA-Met-OH is used in chemical biology research as a chiral amino acid intermediate for constructing probes and labeled methionine-containing scaffolds. The N-formyl group provides a defined amide functionality that can be used to control reactivity during conjugation planning, while the carboxylic acid enables attachment to linkers, solid supports, or coupling handles for probe assembly. The methionine thioether can participate in oxidation-state-dependent labeling strategies or be incorporated into recognition motifs where sulfur chemistry is monitored analytically. FA-Met-OH can be applied to produce biochemical research intermediates for studying peptide behavior, sulfur-related chemical stability, and structure-function relationships in methionine-containing constructs.
5. Analytical Standards And Intermediates
FA-Met-OH is applicable for analytical research and method development where a stereodefined methionine derivative with a controlled protection state is required as a reference standard or calibration component. The combination of formamido and free carboxylic acid groups yields a predictable ionization and chromatographic behavior relative to unprotected methionine, supporting identification of protected amino acid species and monitoring of coupling/deprotection workflows. The sulfur-containing side chain provides an additional structural signature that can be tracked during LC-MS or related analytical assays, including monitoring of oxidation-state changes when relevant. FA-Met-OH can serve as a biochemical research intermediate for validating analytical methods that distinguish methionine derivatives, peptide fragments, and sulfur-modified amino acid analogs.
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