Fmoc-D-Arg(Pmc)-OPfp

Fmoc-D-Arg(Pmc)-OPfp is a D-configuration, N-Fmoc protected arginine derivative bearing a Pmc-protected guanidinium side chain and an OPfp activated ester (pentafluorophenyl ester) at the carboxylate position. The molecule combines a stereogenic center at the amino acid backbone with a highly functionalized side chain that is masked as a Pmc (2,2,5,7,8-pentamethylchroman-6-sulfonyl) guanidine protecting group, while the OPfp handle provides an activated acyl group for peptide coupling chemistry. The Fmoc group supports orthogonal base-labile deprotection during stepwise solid-phase or solution-phase synthesis, and the OPfp ester can participate in acyl transfer reactions under peptide-coupling conditions. The presence of multiple electron-withdrawing fluorine atoms on the leaving group and the protected guanidine motif make the compound a controlled, chiral amino acid building block for downstream synthesis of arginine-containing peptides and related guanidinium-bearing derivatives.

1. Peptide Synthesis

Fmoc-D-Arg(Pmc)-OPfp is used in peptide building block preparation where the Fmoc-protected alpha-amino group and the OPfp activated ester facilitate arginine residue installation during peptide coupling. The Pmc-protected guanidinium side chain suppresses undesired side reactions while maintaining a protected, cationic functionality that can be revealed after peptide assembly. The D-stereochemistry at the backbone enables stereochemically defined incorporation of D-arginine into peptide sequences, including retro-inverso or D-amino acid enriched analogs. The OPfp ester activation supports efficient formation of the corresponding amide linkage, generating protected peptide intermediates that can be carried forward to further chain elongation or final deprotection steps.

2. Bioconjugation Chemistry

Fmoc-D-Arg(Pmc)-OPfp is applicable to bioconjugation workflows that require controlled introduction of a guanidinium-containing motif with orthogonal protecting-group logic. The protected guanidine (Pmc) and the Fmoc group allow sequential deprotection strategies that can be aligned with conjugation timing, minimizing cross-reactivity of the strongly basic side chain during linker attachment. The OPfp ester functionality can be employed to generate acylating intermediates for forming stable amide bonds with amine-bearing biomolecules or linkers, supporting construction of arginine-rich conjugates. The stereodefined D-arginine residue can be used to tune binding, protease resistance, and molecular recognition patterns in labeling and functionalization studies.

3. Protected Amino Acid Chemistry

Fmoc-D-Arg(Pmc)-OPfp serves as a chiral, protected amino acid derivative for orthogonally protected arginine synthesis where both backbone and side-chain masking are required. The Fmoc group provides base-labile N-protection compatible with iterative peptide assembly, while the Pmc group offers side-chain protection suited to maintaining guanidinium integrity through coupling and purification steps. The OPfp activated ester at the carboxylate position enables conversion into peptide-ready acyl species without requiring separate activation reagents, which can simplify process chemistry intermediate preparation. The combination of stereocontrol, side-chain protection, and activated ester reactivity makes the compound suitable for preparing defined arginine-containing intermediates for downstream peptide analog construction and synthetic method development.

4. Peptidomimetics And SAR Studies

Fmoc-D-Arg(Pmc)-OPfp can be incorporated into peptidomimetic and structure-activity relationship (SAR) research where guanidinium presentation and stereochemistry are key determinants of molecular interaction. The protected guanidine side chain supports synthesis of arginine analogs that preserve the cationic character after deprotection, enabling systematic variation of spacing and sequence context in peptide-based scaffolds. The D-arginine backbone stereochemistry can be used to probe how chirality influences receptor-like binding, membrane association, or proteolytic stability in comparative analog series. The residue's protected functional groups allow controlled assembly of libraries of peptide fragments and analogs, supporting SAR-driven optimization of guanidinium-bearing pharmacophores and related molecular designs.

5. Pharmaceutical Manufacturing

Fmoc-D-Arg(Pmc)-OPfp is relevant to pharmaceutical manufacturing of protected peptide intermediates and process-scale synthesis of arginine-containing peptide ingredients. The orthogonal protection scheme, combining Fmoc for alpha-amino protection and Pmc for guanidinium masking, supports predictable deprotection sequencing during manufacturing of defined peptide structures. The OPfp activated ester can function as a coupling-ready carboxylate form, which may integrate into manufacturing routes that rely on activated ester chemistry for amide bond formation under controlled conditions. The stereochemically defined D-arginine residue enables consistent production of stereopure peptide intermediates used in downstream formulation of peptide-based active ingredients or research-grade peptide materials.

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