Fmoc-Glu(OtBu)-OH.H2O

Fmoc-Glu(OtBu)-OH·H2O is an Fmoc-protected glutamic acid derivative provided as a hydrate, where the α-amino group is masked by the base-labile 9H-fluorenylmethoxycarbonyl (Fmoc) protecting group and the side-chain γ-carboxyl functionality is protected as a tert-butyl ester (OtBu). The molecule retains the stereogenic center of glutamate, presenting the (S)-configured amino acid backbone typical of peptide building blocks, and it contains two carboxyl-derived functional sites with orthogonal protection patterns. The presence of the free carboxylic acid at the α-position (-CO2H) and the protected side-chain ester (-CO2tBu) creates a controlled reactivity profile for stepwise coupling and selective deprotection. Hydration can influence handling and crystallization behavior, while the orthogonal Fmoc/OtBu strategy supports downstream conversion to free glutamate side chains for peptide and peptidomimetic construction.

1. Peptide Synthesis

Fmoc-Glu(OtBu)-OH·H2O is employed in peptide synthesis as an orthogonally protected glutamate building block compatible with Fmoc-based solid-phase or solution-phase coupling workflows. The Fmoc group protects the α-amine during chain assembly, while the OtBu ester shields the γ-carboxyl from premature activation, enabling selective formation of the peptide bond at the α-carboxyl/amine interface. Deprotection of the Fmoc moiety can generate a reactive amino terminus for sequential elongation, and later removal of the OtBu group can reveal the side-chain carboxyl for salt formation, hydrogen-bonding interactions, or further functionalization. The resulting glutamate-containing peptides and peptide fragments can be used for sequence-defined studies, linker design, and generation of acidic side-chain motifs in biomolecular scaffolds.

2. Side-Chain Functionalization

Fmoc-Glu(OtBu)-OH·H2O supports amino acid derivatization and side-chain engineering through its protected γ-carboxyl ester, which can be selectively unmasked after peptide coupling or during intermediate preparation. The glutamate side-chain carboxyl provides a handle for forming amide, ester, or activated-carboxyl derivatives, enabling attachment of solubilizing groups, affinity tags, or reactive moieties used in chemical biology and materials-oriented conjugation strategies. Orthogonal protection helps maintain the α-functional region during selective transformations, supporting controlled installation of functional groups at the γ-position without perturbing the peptide backbone. Downstream products include glutamate-modified peptides, peptidomimetic fragments, and functional intermediates for constructing acidic, charge-tunable molecular architectures.

3. Protected Amino Acid Chemistry

Fmoc-Glu(OtBu)-OH·H2O is suitable for protected amino acid synthesis and chiral intermediate preparation where orthogonal deprotection logic is required to manage multiple carboxyl-derived functionalities. The Fmoc group provides base-labile protection of the α-amine, while the OtBu ester offers acid-labile masking of the side-chain carboxyl, enabling sequential unmasking and predictable reactivity control. The hydrate form can be used as a practical feedstock for manufacturing routes that require consistent handling of amino acid derivatives, while the stereodefined glutamate backbone maintains chiral integrity through downstream transformations. The compound can serve as a starting material for producing glutamate derivatives used in peptide building block libraries, process-scale intermediate supply, and fine chemical synthesis of protected amino acid reagents.

4. Chemical Biology And Conjugation

Fmoc-Glu(OtBu)-OH·H2O is applied in chemical biology workflows that require incorporation of glutamate residues into probes, linkers, and conjugation-ready peptide constructs. The protected side-chain carboxyl allows controlled introduction of an acidic functionality that can participate in ionic interactions, influence local conformation, and serve as a platform for coupling chemistry after deprotection. Fmoc-based handling supports stepwise assembly of defined sequences, which can then be converted into biomolecule conjugates through activation of the revealed carboxyl group or through further derivatization to amide-forming partners. Downstream uses include generation of peptide-based labeling reagents, affinity ligands, and molecular tools where glutamate charge and geometry are used to tune binding and solubility behavior.

5. Pharmaceutical Manufacturing Intermediates

Fmoc-Glu(OtBu)-OH·H2O can be utilized in pharmaceutical manufacturing contexts as a process-relevant protected amino acid intermediate for producing peptide active pharmaceutical ingredient (API) precursors and peptide-like intermediates. The orthogonal Fmoc/OtBu protection scheme supports manufacturing-compatible step sequencing: Fmoc deprotection to expose the amine for coupling, followed by OtBu removal to regenerate the side-chain carboxyl for subsequent transformations or final product specification. The defined stereochemistry of glutamate and the presence of two carboxyl-derived sites enable consistent incorporation into sequence-defined intermediates used during scale-up of peptide synthesis. The compound thereby functions as a controllable input for industrial peptide construction, intermediate standardization, and downstream derivatization steps that depend on orthogonally protected functional groups.

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