Fmoc-Ser(PO3H2)-OH is an Fmoc-protected serine derivative bearing a phosphonic acid substituent on the side chain, classifying it as a modified, proteinogenic amino acid analogue used for peptide-related synthesis. The molecule contains an Fmoc carbamate protecting group on the α-amino functionality, a free carboxylic acid, and a side-chain phosphonic acid (PO3H2) that provides strong anionic character and can participate in salt formation and hydrogen-bonding interactions. In synthesis and chemical biology workflows, it is employed as a stepwise building block for introducing a phosphorylated serine mimic into peptides and peptide conjugates, supporting structure-function studies and analytical method development involving phospho-serine-like motifs.
Fmoc-Ser(PO3H2)-OH is an Fmoc-protected serine derivative bearing a side-chain phosphonic acid group in a defined stereochemical context consistent with serine amino acid chemistry. The molecule contains the Fmoc carbamate for orthogonal amine protection, a free carboxylic acid for C-terminal compatibility, and a phosphonic acid functionality (PO3H2) that is strongly polar, can exist in equilibrium with mono- and dianionic forms, and participates in coordination and hydrogen-bonding interactions. The presence of the phosphonic acid on the side chain makes the compound a chemically distinct protected amino acid building block for incorporating phosphoserine motifs into peptides and for preparing phosphorylated or phosphonate analogs under controlled deprotection and coupling conditions. The combination of an acid-labile peptide handle (Fmoc) and a robust phosphonate/acid functionality supports downstream synthetic utility in peptide science, biochemical probe construction, and process-oriented intermediate preparation.
1. Phosphoserine Peptide Synthesis
Fmoc-Ser(PO3H2)-OH is applied in phosphoserine-containing peptide building workflows where side-chain acidic functionality must be introduced with stereochemical fidelity to the serine scaffold. The Fmoc-protected amino group and the free carboxylic acid enable standard peptide coupling logic for N-to-C assembly, while the PO3H2 side chain provides a phosphorylation-mimetic handle that can be carried through peptide assembly or converted into related phosphate/phosphonate forms depending on the chosen downstream strategy. The phosphonic acid group can influence coupling and purification behavior through charge effects, making it compatible with research-grade peptide synthesis routes that explicitly manage acidic residues and ionizable side chains. The resulting peptide products support studies of phospho-dependent recognition, kinase-substrate motif mapping, and phosphoserine analog construction for biomolecular recognition assays.
2. Chemical Biology Probes
Fmoc-Ser(PO3H2)-OH is used in chemical biology research to generate phosphoserine-mimicking probes for investigating protein-ligand interactions and phospho-site recognition. The side-chain phosphonic acid provides a strong anionic motif that can engage metal ions and form defined electrostatic and hydrogen-bonding patterns, while the serine backbone maintains the spatial relationship expected for phosphoserine-like recognition. The Fmoc group supports controlled incorporation into peptide or peptidomimetic frameworks, allowing probe synthesis with orthogonal handling of the amine and carboxyl functionalities. Downstream derivatization can leverage the PO3H2 group for conjugation chemistry, enabling the preparation of labeled or affinity-tagged biomolecular constructs for mechanistic studies and binding characterization.
3. Peptidomimetic And SAR Studies
Fmoc-Ser(PO3H2)-OH is suitable for peptidomimetic construction in structure-activity relationship (SAR) investigations where phosphoserine-like electrostatics are tuned while maintaining an amino acid-derived scaffold. The compound's serine-derived backbone supports incorporation into short peptide analogs, and the PO3H2 side chain serves as a phosphonate/phosphorylation mimic that can modulate conformation and binding through persistent negative charge. Fmoc protection enables iterative assembly of analog libraries, and the carboxylic acid functionality supports C-terminal modification strategies that can be used to probe how terminal charge and hydrogen-bonding affect molecular recognition. The resulting phosphoserine-mimetic series can be employed as research intermediates for SAR mapping, fragment elaboration, and molecular design workflows targeting phospho-dependent binding interfaces.
4. Bioconjugation and Biomolecule Labeling
Fmoc-Ser(PO3H2)-OH is applied in bioconjugation contexts where phosphonic acid functionality is used to introduce charge-defined recognition elements onto biomolecule scaffolds. The PO3H2 group can function as a chemically stable, strongly polar motif for attaching or templating biomolecular conjugates, while the Fmoc-protected amine and carboxyl group allow the compound to be incorporated into peptide linkers that later undergo deprotection or coupling to larger biomolecular targets. The phosphonic acid's ability to coordinate metal ions and engage in electrostatic interactions can be exploited in affinity labeling designs and in constructing conjugates that require controlled presentation of anionic groups. Downstream utility includes preparation of peptide-based linkers, phosphoserine-mimetic tags, and analytical standards used to validate labeling strategies and conjugate identity in biochemical workflows.
5. Process Chemistry Intermediate Preparation
Fmoc-Ser(PO3H2)-OH is relevant to process chemistry intermediate preparation for manufacturing phosphoserine-containing peptide reagents and phosphonate-bearing building blocks. The molecule's orthogonal protection pattern, combining an Fmoc-protected amine with a side-chain PO3H2 acid functionality, supports route design that separates amine deprotection steps from handling of the phosphonic acid group. The presence of both an Fmoc carbamate and a free carboxylic acid provides defined functional handles for purification and conversion into downstream peptide coupling-ready forms in controlled chemical manufacturing sequences. Industrially oriented use can include synthesis of phosphoserine-mimetic peptide fragments, preparation of charged amino acid derivatives for automated peptide production, and supply of chiral amino acid intermediates that retain the serine stereochemical framework for consistent downstream assembly.
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