Fmoc-Gln-OPfp

Fmoc-Gln-OPfp is an Fmoc-protected glutamine derivative bearing a C-terminal OPfp ester (pentafluorophenyl ester) that encodes both an amino acid backbone and an activated carboxylate for downstream coupling chemistry. The molecule contains an Fmoc carbamate on the α-amino group, a side-chain amide characteristic of glutamine, and a stereodefined α-carbon consistent with the natural amino acid configuration used in peptide synthesis. The OPfp group provides a highly leaving-group-enabled ester functionality that can participate in rapid acyl-transfer and peptide coupling strategies under standard peptide chemistry conditions, while the pentafluorophenyl moiety also supports analytical detectability and reactivity tuning. The combination of orthogonally removable Fmoc protection and an activated ester handle makes Fmoc-Gln-OPfp a practical chiral amino acid intermediate for constructing amide-rich targets and for preparing glutamine-containing peptide segments with controlled N-terminus identity.

1. Peptide Synthesis

Fmoc-Gln-OPfp is applied in peptide building-block preparation where Fmoc removal and subsequent amide bond formation are central to solid-phase or solution-phase assembly. The protected α-amino group as an Fmoc carbamate enables selective N-deprotection while the OPfp ester functions as an activated C-terminal acyl source for peptide coupling to incoming amines. The glutamine side-chain amide can remain compatible with standard peptide workflows, supporting incorporation of Gln residues into sequences that require side-chain hydrogen-bonding patterns. The OPfp activation can facilitate formation of peptide bonds under coupling conditions that rely on activated carboxylates, supporting the construction of glutamine-containing fragments used in peptide library synthesis and sequence optimization. Fmoc-Gln-OPfp thus serves as an amino acid ester intermediate tailored for peptide coupling chemistry and downstream peptide analog generation.

2. Protected Amino Acids

Fmoc-Gln-OPfp is utilized as an orthogonally protected amino acid derivative in protected amino acid synthesis, combining an Fmoc-protected amine with a C-terminal OPfp ester handle. The Fmoc group provides a stable N-protection strategy during intermediate handling, while the OPfp ester offers a distinct reactivity profile relative to unactivated carboxylic acids, enabling controlled conversion into amide linkages. The side-chain amide of glutamine remains a functional group that can be carried through coupling steps and later used for further derivatization, such as selective transformation to side-chain-modified glutamine analogs. The stereochemical integrity at the α-carbon supports predictable peptide stereochemistry in assembled products. Fmoc-Gln-OPfp therefore functions as a chiral, protected amino acid intermediate that aligns with orthogonal protection and activated ester chemistry used in synthetic peptide manufacturing.

3. Chemical Biology Labeling

Fmoc-Gln-OPfp is suitable for chemical biology research that requires glutamine incorporation into peptide probes and affinity reagents through robust amide coupling. The Fmoc-protected amine and the activated OPfp ester enable conversion into peptide conjugates where the glutamine residue contributes polar side-chain functionality for molecular recognition and solubility tuning. The OPfp ester can be leveraged to form amide bonds with amine-bearing targeting motifs, while the glutamine side-chain amide can participate in hydrogen-bond networks that influence binding and conformational preferences of peptide-based ligands. The resulting glutamine-containing constructs can be used to generate substrates for biochemical assays, immobilized capture reagents, or probe scaffolds for studying protein-peptide interactions. Fmoc-Gln-OPfp thereby supports amino acid derivatization workflows that connect protected amino acid chemistry to downstream biomolecule modification.

4. Peptidomimetics And SAR Studies

Fmoc-Gln-OPfp is employed in peptidomimetic construction and structure-activity relationship studies where glutamine-like amide functionality is used to tune binding interactions. The compound's α-amide-forming capacity via OPfp activation supports incorporation of glutamine residues into peptide analogs and constrained scaffolds used to map the role of side-chain hydrogen bonding. The Fmoc protection strategy allows controlled assembly of N-terminus-defined analogs, supporting systematic variation of sequence context around the glutamine unit. The glutamine side-chain amide can be retained to preserve key polar contacts or can serve as a handle for later chemical modification to generate SAR-focused analog series. Fmoc-Gln-OPfp thus functions as a stereodefined amino acid intermediate enabling peptide science and medicinal chemistry-style derivatization of glutamine-containing motifs.

5. Process Chemistry Intermediate

Fmoc-Gln-OPfp is relevant to process chemistry and fine chemical synthesis as an activated amino acid ester intermediate that can streamline peptide coupling operations by using a leaving-group-rich OPfp moiety. The orthogonal combination of Fmoc protection on nitrogen and OPfp activation on the carboxylate supports a manufacturing logic that separates deprotection events from coupling events, aiding route design for glutamine-containing intermediates. The presence of a single activated ester functionality can reduce variability associated with carboxylic acid activation steps, supporting reproducible acyl transfer to amine partners during intermediate preparation. The glutamine side-chain amide remains chemically stable under typical peptide synthesis conditions, enabling consistent downstream conversion into peptide fragments or conjugates. Fmoc-Gln-OPfp therefore serves as a practical chiral building block for industrial peptide intermediate preparation and controlled synthesis of amide-rich products.

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