Fmoc-L-Ser(PO(OBzl)OH)-OH

Fmoc-L-Ser(PO(OBzl)OH)-OH is an Fmoc-protected L-serine derivative bearing a side-chain phosphonic acid esterified with a benzyloxymethyl (OBzl) group, resulting in a chiral amino acid intermediate with a protected N-terminus and a partially protected phosphate functionality. The molecule contains the Fmoc carbamate on the amino group, a free carboxylic acid at the C-terminus, and a phosphonic acid motif (P-OH) that can participate in acid-base equilibria and phosphorylation-mimetic chemistry. Benzyl protection on the phosphate oxygen provides orthogonal handling relative to peptide coupling conditions, while the serine side-chain linkage positions the phosphorus substituent for incorporation into peptide backbones and peptide-like constructs. The presence of both a nucleophilic phosphonic acid and a protected amino acid framework makes the compound suitable for controlled deprotection sequences that reveal reactive phosphate groups for downstream derivatization and biochemical research.

1. Peptide Synthesis

Fmoc-L-Ser(PO(OBzl)OH)-OH is used in peptide synthesis workflows that require phosphorylation-mimetic or phospho-functional serine residues within protected amino acid building blocks. The Fmoc carbamate enables standard base-mediated N-terminal deprotection during solid-phase peptide assembly, while the C-terminal carboxylic acid supports peptide coupling to adjacent residues. The side-chain serine oxygen positions the phosphonic acid group for incorporation as a stable phosphate analog, and the OBzl group can be managed through orthogonal deprotection to control the timing of phosphate unveiling. Phosphorylated peptide analogs generated from this intermediate can be applied to mapping phosphorylation-dependent recognition motifs and to constructing peptide scaffolds bearing defined anionic charge distribution.

2. Chemical Biology

Fmoc-L-Ser(PO(OBzl)OH)-OH serves chemical biology studies that investigate phosphorylation signaling and protein-peptide recognition using non-hydrolyzable or conformationally constrained phosphate mimics. The phosphonic acid (P-OH) on the serine side chain provides a strongly hydrogen-bonding, anionic character that can reproduce key electrostatic interactions seen in phosphoserine motifs. The Fmoc-protected amino acid framework supports incorporation into longer peptide sequences, enabling systematic variation of neighboring residues while maintaining a consistent phosphate-like functional group. OBzl protection supports stepwise synthesis and later conversion to a more reactive or fully deprotected phosphonic acid form for probing binding specificity, phosphatase resistance, and kinase-substrate mimicry in biochemical research contexts.

3. Bioconjugation Chemistry

Fmoc-L-Ser(PO(OBzl)OH)-OH is applicable to bioconjugation strategies where phosphate-bearing linkers or phosphorylated peptide handles are required for controlled attachment to biomolecules. The free phosphonic acid functionality can participate in coordination, hydrogen bonding, and selective coupling chemistries after appropriate activation, while the serine scaffold provides a defined spatial presentation relative to the peptide backbone. The Fmoc group supports peptide-level assembly prior to conjugation, allowing the phosphonic acid to be introduced at a chosen position within a peptide tag or targeting motif. OBzl protection enables manufacturing-style control of functional group exposure, supporting downstream formation of phosphate-functional conjugates used for biomolecule labeling, affinity probes, and analytical reagent construction.

4. SAR Studies

Fmoc-L-Ser(PO(OBzl)OH)-OH is suitable for structure-activity relationship studies that require systematic evaluation of phosphoserine analogs in peptide-based molecular recognition. The chiral L-serine backbone ensures stereochemical fidelity at the amino acid center, while the side-chain phosphonic acid provides a tunable anionic group that can influence binding orientation and electrostatic complementarity. The protected phosphate oxygen (OBzl) enables reproducible synthesis of libraries where phosphate deprotection or further functionalization can be synchronized across analog series. Peptide analogs prepared from this intermediate can be used to correlate residue-level changes with recognition outcomes in SAR workflows for phospho-dependent binding interfaces and peptide-mimetic design.

5. Process Chemistry Intermediate

Fmoc-L-Ser(PO(OBzl)OH)-OH functions as a process chemistry intermediate for the manufacture of protected phosphoserine building blocks and phosphorylated peptide reagents at scale. The orthogonal protection pattern, combining an Fmoc-protected amine with a benzyl-protected phosphate oxygen, supports controlled stepwise processing where peptide coupling conditions and later phosphate deprotection can be separated by reagent compatibility. The presence of a single stereogenic center and a defined carboxylic acid simplifies downstream conversion into activated coupling forms for peptide assembly or into fully deprotected phosphonic acid derivatives for further chemical transformations. Industrial synthesis routes can leverage the stable protected phosphate functionality to reduce premature side reactions, enabling reliable preparation of phosphorylated amino acid derivatives used in fine chemical production and specialty reagent manufacturing.

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