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

Fmoc-L-Thr(PO(OBzl)OH)-OH is an Fmoc-protected L-threonine derivative bearing a side-chain phosphoric acid monoester in which the phosphate is substituted with a benzyloxybenzyl (OBzl) group and a free hydroxyl-bearing phosphoryl moiety. The molecule combines a stereogenic threonine center with an anionic, hydrogen-bonding-capable phosphate group that can participate in hydrogen bonding and acid-base equilibria while remaining compatible with peptide coupling workflows when appropriately protected. The Fmoc carbamate on the alpha-amino group provides orthogonal base-labile protection for solid-phase peptide synthesis, whereas the benzyloxybenzyl substituent on phosphorus functions as a strategy to manage phosphate reactivity during chain assembly. The presence of a free phosphoric OH enables downstream phosphorylation-state tuning, selective deprotection, and conversion into phosphate-linked motifs used in biochemical research and synthetic chemistry.

1. Peptide Synthesis

Fmoc-L-Thr(PO(OBzl)OH)-OH supports peptide building block preparation for solid-phase peptide synthesis where threonine phosphorylation is required at a defined position. The Fmoc-protected amino group enables standard peptide coupling chemistry, while the side-chain phosphate monoester is engineered to reduce uncontrolled side reactions during chain elongation. The benzyloxybenzyl phosphate substituent helps maintain the integrity of the phosphoryl functionality under conditions used to remove Fmoc and extend the peptide chain, enabling incorporation of a phosphorylated threonine residue into peptide sequences. The resulting phosphorylated peptide analogs can be used as substrates, standards, or reference scaffolds for studying phosphorylation-dependent recognition and synthetic peptide structure-function relationships.

2. Chemical Biology

Fmoc-L-Thr(PO(OBzl)OH)-OH is suitable for chemical biology workflows that require controlled installation of a phosphothreonine motif in peptide ligands and molecular probes. The stereochemically defined threonine backbone and the free phosphate hydroxyl support specific hydrogen-bonding patterns and electrostatic interactions that mimic phosphorylation states in protein environments. The orthogonal protection scheme, combining Fmoc on nitrogen with a benzyl-protected phosphate substituent, enables sequential manipulation of the peptide and phosphorylation chemistry to generate defined phosphoforms for binding and recognition studies. Phosphothreonine-containing peptides prepared from this amino acid derivative can be applied in receptor-ligand mapping, phospho-dependent interaction assays, and mechanistic investigations of phosphorylation signaling at the molecular level.

3. Bioconjugation Chemistry

Fmoc-L-Thr(PO(OBzl)OH)-OH can be employed to construct phosphorylated linkers and conjugation handles for biomolecule modification where phosphate-mediated binding or charge presentation is desired. The phosphoryl group bearing a protected OBzl substituent can be carried through peptide assembly as a functional group that later undergoes deprotection or further transformation to yield a reactive phosphate state for coupling into larger constructs. The Fmoc-protected amino functionality allows incorporation into peptide scaffolds that can subsequently be functionalized for attachment to proteins, polymers, or surfaces through orthogonal chemistries. Downstream derivatives derived from this building block can serve as phosphorylated conjugates for studying biomolecular recognition, surface immobilization of phospho-motifs, and charge-driven assembly in applied biochemical research.

4. Peptidomimetics And SAR

Fmoc-L-Thr(PO(OBzl)OH)-OH is applicable to peptidomimetic and structure-activity relationship studies where a phosphothreonine element must be positioned with stereochemical fidelity. The protected phosphate monoester provides a handle for generating phospho-mimetic analogs or for producing peptides that retain a defined phosphorylation geometry during synthesis and purification. The combination of an Fmoc-protected alpha-amino group and a managed side-chain phosphate supports systematic variation of neighboring residues while keeping the phosphoryl group chemically addressable for later transformations. Phosphorylated threonine-containing analog libraries derived from this intermediate can be used to probe binding site requirements, phosphorylation-dependent selectivity, and SAR trends across closely related peptide scaffolds.

5. Process Chemistry Intermediate

Fmoc-L-Thr(PO(OBzl)OH)-OH serves as a chiral, protected amino acid intermediate for process chemistry and fine chemical synthesis routes targeting phosphorylated amino acid building blocks. The molecule's orthogonal protection pattern, with base-labile Fmoc and phosphate protection via OBzl substitution, supports manufacturing workflows that require staged deprotection, controlled handling of anionic groups, and predictable downstream conversion to phosphorylated derivatives. The presence of a stereogenic threonine center and a functional phosphate hydroxyl enables conversion into alternative phosphate-protected forms or into phosphorylated peptide fragments used in larger-scale peptide manufacture. Industrially relevant use cases include preparation of protected phosphoamino acid reagents for peptide manufacturing, synthesis of phosphorylated intermediates for specialty chemical production, and generation of well-defined phosphothreonine-containing materials for research-grade supply chains.

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