Fmoc-[ring-D5]Phe-OH is an Fmoc-protected, deuterium-labeled phenylalanine derivative in which the phenyl ring bears five deuterium atoms, retaining the amino acid backbone for incorporation into peptide-building chemistry. The molecule contains a free carboxylic acid (-COOH) and an Fmoc-protected amino group (carbamate), with the aromatic side chain providing a hydrophobic phenyl functionality while the ring deuteration supports isotopic labeling for mass-based analysis. In synthesis and analytical workflows, it is employed as a protected amino acid building block for stepwise peptide assembly and as a stable-isotope tracer to enable LC-MS or MS/MS discrimination of phenylalanine-containing fragments and to support structure-activity or labeling studies.
Fmoc-[ring-D5]Phe-OH is an Fmoc-protected, deuterium-labeled phenylalanine derivative in which five deuterium atoms are incorporated specifically into the aromatic ring, preserving the chiral amino acid stereocenter at the alpha carbon. The molecule combines an Fmoc carbamate for temporary N-protection with a free carboxylic acid for orthogonal coupling chemistry, enabling controlled peptide building-block use while maintaining the labeled side chain for spectroscopic discrimination. The aromatic deuteration pattern shifts vibrational and mass signatures, supporting quantitative tracking in analytical workflows and mechanistic studies of aromatic-group transformations. The defined isotopic labeling and protected amine functionality make the compound suitable as a chiral, isotope-tagged intermediate for peptide synthesis and downstream synthetic derivatization.
1. Isotope-Labeled Peptide Synthesis
Fmoc-[ring-D5]Phe-OH is applied in peptide synthesis workflows where isotopic labeling is required for mass spectrometric quantification and site-specific tracing. The Fmoc-protected N-terminus enables standard solid-phase or solution-phase peptide coupling after deprotection, while the free carboxylic acid participates in amide bond formation to install the ring-D5 phenylalanine residue into growing peptide chains. Aromatic ring deuteration provides a distinct mass shift and altered fragmentation behavior, supporting unambiguous identification of labeled peptides, including during purification and method development. Incorporation into peptide building blocks supports biochemical research intermediate preparation for studies that require controlled labeling at a defined position within a peptide scaffold.
2. Mass Spectrometry Standards
Fmoc-[ring-D5]Phe-OH is used for analytical research as an isotopically defined amino acid and peptide precursor for calibration standards and internal reference materials. The ring-D5 substitution creates predictable mass differences relative to unlabeled phenylalanine, improving selectivity in LC-MS and MS/MS-based quantitation of aromatic-containing targets. The Fmoc group can be removed to generate the corresponding labeled amino acid for derivatization strategies, or the protected form can be incorporated into short peptides that behave consistently during chromatographic separation. Isotopically anchored fragments derived from this building block can serve as anchors for method validation, impurity profiling, and structural confirmation in chemical and biochemical characterization pipelines.
3. Peptidomimetic And SAR Studies
Fmoc-[ring-D5]Phe-OH supports structure-activity relationship studies and peptidomimetic construction where aromatic side-chain identity and position-specific labeling enable mechanistic interpretation. The phenylalanine backbone provides a stereochemically defined alpha-amino acid framework, while the ring-D5 aromatic label allows tracking of aromatic participation in binding, metabolism-relevant transformations, or chemical stability assays without altering the overall substitution pattern. Fmoc protection facilitates incorporation into peptide analogs using peptide coupling chemistries, enabling systematic generation of labeled analog series for comparative studies. Downstream, the labeled aromatic residue can be carried through to non-natural scaffolds, supporting fragment-based molecular design and rational modification strategies that rely on isotopic discrimination.
4. Process Chemistry Intermediate Preparation
Fmoc-[ring-D5]Phe-OH is suitable for process chemistry intermediate preparation where isotopically labeled amino acid derivatives must be manufactured reproducibly for downstream fine chemical synthesis. The combination of Fmoc N-protection and a free carboxylic acid provides an orthogonal functional-group set that can be handled through protection/deprotection steps and coupling operations without requiring alteration of the deuterated aromatic ring. Ring-D5 labeling improves detectability of intermediates and final labeled materials, which can be leveraged for in-line or end-point analytical confirmation during manufacturing route design. The compound thereby functions as a controlled chiral, isotope-tagged feedstock for producing labeled peptide building blocks and related amino acid derivatives at scale.
5. Chemical Biology Labeling
Fmoc-[ring-D5]Phe-OH is used in chemical biology research to enable site-specific labeling of aromatic residues in peptide-based probes and biomolecule conjugates. The Fmoc-protected amine and carboxylic acid allow controlled installation into peptide sequences that can later be functionalized at termini or side-chain handles, aligning with common conjugation strategies that depend on orthogonal reactive groups. The ring-D5 aromatic label provides a chemically stable isotopic tag that can be detected by mass spectrometry, supporting localization of labeled moieties in complex mixtures such as digests or binding assays. The resulting labeled peptide or peptidic conjugate serves as a biochemical research intermediate for studying molecular recognition, turnover, and transformation pathways in systems where aromatic-group tracking is required.
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