Fmoc-Asp(OtBu)-OPfp

Fmoc-Asp(OtBu)-OPfp is an Fmoc-protected aspartic acid derivative bearing an O-tert-butyl side-chain ester and an activated pentafluorophenyl (OPfp) ester at the carboxylate position, providing a chiral, orthogonally protected amino acid building block for peptide coupling and downstream acyl transfer chemistry. The molecule combines an Fmoc carbamate on the α-amino group with a tert-butyl-protected β-carboxylate motif, while the OPfp group introduces a leaving group that can participate in nucleophilic acyl substitution under peptide-synthesis compatible conditions. The presence of multiple protecting groups enables controlled deprotection sequences and selective functional group manipulation, including conversion to amide linkages or further derivatization of the aspartate side chain. The pentafluorophenyl ester functionality also supports high reactivity toward amine nucleophiles, making the compound suitable for preparing peptide fragments, activated intermediates, and acylated derivatives in both research and industrial fine-chemical workflows.

1. Peptide Coupling

Fmoc-Asp(OtBu)-OPfp is applied in peptide synthesis workflows where activated carboxylate chemistry is required for efficient amide bond formation. The Fmoc-protected α-amino group supports standard solid-phase or solution-phase peptide assembly after base-mediated Fmoc removal, while the OPfp ester at the aspartate carboxylate can undergo acyl substitution with peptide amines to generate the corresponding aspartyl linkage. The tert-butyl group on the side-chain carboxylate provides orthogonal protection, allowing selective deprotection later to reveal the β-carboxyl functionality for subsequent coupling or post-assembly modification. The resulting aspartate-containing peptide segments can be used to build sequence-defined peptides and peptide libraries that require controlled side-chain carboxyl handling.

2. Protected Amino Acid Chemistry

Fmoc-Asp(OtBu)-OPfp serves as a protected amino acid intermediate for derivatization strategies that depend on orthogonal protecting-group logic. The combination of Fmoc on the α-amine and tert-butyl on the β-carboxylate enables stepwise deprotection, while the OPfp ester provides a reactive handle for converting the carboxylate into amide or related acyl derivatives without immediately exposing free carboxylic acids. The stereochemical integrity of the aspartate backbone is maintained through its use as a chiral building block, supporting stereochemically consistent peptide and peptidomimetic construction. The compound can be employed to prepare activated aspartate fragments, acylated intermediates for fragment coupling, and protected derivatives used in iterative synthesis toward complex amino acid-based targets.

3. Peptidomimetic Construction

Fmoc-Asp(OtBu)-OPfp is suitable for peptidomimetic and constrained scaffold synthesis where aspartate-like carboxylate geometry and side-chain functionality influence molecular recognition. The OPfp ester can be used to install the aspartyl carbonyl onto amine-bearing fragments, while the tert-butyl-protected side chain helps preserve the β-carboxylate during assembly of non-natural linkers and modified backbones. The Fmoc group supports controlled introduction into peptide-like sequences and can be removed to enable further coupling steps or incorporation into hybrid materials. The resulting intermediates support construction of structure-activity relationship (SAR) focused analog series where the aspartate side-chain carboxylate is retained for later deprotection or functional transformation.

4. Bioconjugation Chemistry

Fmoc-Asp(OtBu)-OPfp can be applied in bioconjugation and chemical biology workflows that require site-specific acylation of amine-containing biomolecules or linkers. The pentafluorophenyl ester is a strong acylating motif that can react with nucleophilic amines to form stable amide bonds, enabling attachment of aspartate-derived handles onto peptides, proteins, or carrier molecules bearing primary amine groups. The tert-butyl protection can be used to control whether the β-carboxylate remains masked during conjugation, supporting downstream deprotection to generate anionic sites for further coupling, chelation, or electrostatic tuning. The Fmoc group can also be leveraged to manage compatibility with peptide-derived conjugation strategies, supporting the preparation of defined conjugates and analytical standards for monitoring conjugation chemistry.

5. Process Chemistry Intermediate

Fmoc-Asp(OtBu)-OPfp is relevant to process chemistry and specialty chemical production as an activated amino acid derivative that can be integrated into scalable peptide intermediate manufacturing. The OPfp ester provides an operationally practical activation mode for converting carboxylate functionality into acylated products, while the orthogonal Fmoc and tert-butyl protecting groups support controlled downstream transformations and reduce cross-reactivity during multi-step syntheses. The compound's protected structure aligns with industrial peptide building block preparation, where minimizing premature deprotection and maintaining side-chain integrity are key to reproducible manufacturing routes. The resulting aspartate ester intermediates can be used to produce peptide fragments, activated coupling reagents, and protected acyl derivatives that feed directly into larger-scale fine chemical synthesis and industrial peptide supply chains.

6. Analytical Research Standards

Fmoc-Asp(OtBu)-OPfp is suitable for analytical research and method development requiring well-defined, protected aspartate-containing standards. The presence of Fmoc enables sensitive detection and chromatographic behavior consistent with Fmoc-tagged amino acid derivatives, supporting LC-MS or HPLC method calibration for protected amino acids and peptide intermediates. The OPfp ester and tert-butyl side-chain protection provide identifiable chemical signatures that can be tracked during synthesis, deprotection, or acylation steps, assisting in impurity profiling and reaction monitoring. The compound can be employed to generate reference materials for verifying peptide coupling outcomes, confirming side-chain protection status, and supporting quality control of aspartate-containing peptide building blocks in biochemical research and industrial manufacturing environments.

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