Fmoc-Asn(Mtt)-OPfp

Fmoc-Asn(Mtt)-OPfp is an N-Fmoc protected asparagine derivative bearing an Mtt-protected side-chain amide and an OPfp ester at the C-terminus, combining three orthogonal functional handles for peptide chemistry and downstream transformations. The asparagine stereocenter is retained in the amino acid backbone, while the Fmoc group provides base-labile N-protection for stepwise solid-phase or solution-phase assembly. The Mtt (mittert-butylthio) protecting group on the side-chain amide nitrogen is designed to withstand common coupling conditions yet can be removed under selective conditions, enabling controlled side-chain deprotection and subsequent amide/urea/linked functionality formation. The OPfp ester (pentafluorophenyl ester) imparts high acyl-transfer reactivity for rapid formation of peptide bonds or for generating activated intermediates in synthetic organic chemistry.

1. Peptide Synthesis

Fmoc-Asn(Mtt)-OPfp is used in peptide building workflows where an Fmoc-protected amino acid with an activated C-terminus supports efficient peptide coupling strategies. The Fmoc group enables iterative N-terminal deprotection and re-protection cycles, while the OPfp ester can participate in acyl transfer to form amide linkages under standard peptide coupling conditions. The Mtt-protected asparagine side-chain amide maintains orthogonality during chain elongation, reducing undesired side reactions from the polar side-chain functionality. The resulting protected asparagine residue is suitable for constructing peptides that require later side-chain unveiling for hydrogen-bonding pattern control, selective conjugation, or incorporation into asparagine-dependent recognition motifs.

2. Protected Amino Acids

Fmoc-Asn(Mtt)-OPfp serves as a protected amino acid intermediate for orthogonally protected amino acid synthesis, derivatization, and late-stage functional group manipulation. The combination of N-Fmoc protection, Mtt-protected side-chain amide, and OPfp activation provides a controlled reactivity profile that can be tuned by selective deprotection or activation steps. The OPfp ester functionality supports conversion into peptide-ready acyl species, while the protected side-chain amide allows downstream transformations such as selective deprotection to regenerate the native asparagine side chain or to enable controlled formation of substituted amides. The stereochemically defined asparagine backbone makes the compound compatible with stereocontrolled assembly of peptide analogs and with synthetic routes that require predictable functional group placement.

3. Bioconjugation Chemistry

Fmoc-Asn(Mtt)-OPfp can be applied in chemical biology workflows where protected asparagine residues are introduced as handles for conjugation and site-specific labeling strategies. The Mtt-protected side-chain amide provides a masked polar functional group that can be selectively unmasked to generate a reactive amide site for subsequent coupling chemistry, including formation of urea-like linkages or attachment of substituents that preserve side-chain hydrogen-bonding characteristics. The Fmoc group supports controlled incorporation into peptide scaffolds prior to conjugation, enabling generation of defined conjugation points within larger biomolecular constructs. The OPfp ester can also function as an activated acyl intermediate for preparing conjugation-ready derivatives, supporting downstream synthesis of labeled peptides, probe molecules, or modular bioconjugation reagents used in biochemical research.

4. SAR Studies

Fmoc-Asn(Mtt)-OPfp is suitable for structure-activity relationship studies that rely on systematic variation of asparagine-containing peptide fragments and peptidomimetic scaffolds. The protected side-chain amide allows consistent handling during synthesis of peptide libraries, while selective deprotection supports generation of analogs with defined side-chain availability for receptor or protein interaction mapping. The Fmoc strategy facilitates parallel assembly of multiple analogs with controlled N-terminal identity, and the OPfp ester supports reliable peptide bond formation during library construction. The resulting asparagine-bearing intermediates can be used to generate SAR panels where side-chain polarity and hydrogen-bonding geometry are tuned while maintaining stereochemical fidelity across analog series.

5. Pharmaceutical Manufacturing

Fmoc-Asn(Mtt)-OPfp can be employed in industrial peptide manufacturing contexts as a protected amino acid building block for producing defined asparagine-containing intermediates used in process chemistry. The orthogonal protection pattern, featuring base-labile Fmoc and selectively removable Mtt on the side-chain amide, supports manufacturing sequences that require predictable deprotection timing and minimized side reactions during repeated coupling cycles. The OPfp ester activation mode can be leveraged to design robust acylation steps that translate from development to scale while maintaining compatibility with peptide synthesis equipment and controlled workup operations. The stereochemically constrained asparagine residue and the protected side-chain functionality support downstream formation of peptide intermediates used for further processing, purification, and formulation into industrially manufactured peptide materials.

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