Fmoc-Arg(Me)2-OH (asymmetrical)

Fmoc-Arg(Me)2-OH (asymmetrical) is an Fmoc-protected arginine derivative bearing an asymmetrically substituted guanidino side chain with two methyl groups on the terminal nitrogen environment, preserving a stereogenic α-carbon typical of arginine-based peptide building blocks. The molecule combines an Fmoc carbamate on the α-amino group with a free carboxylic acid, enabling controlled N-terminus protection while maintaining a reactive C-terminus for coupling or conversion to activated derivatives. The substituted guanidinium functionality exhibits strong basicity and hydrogen-bonding capacity, while the methylation pattern can modulate solubility, ion-pairing behavior, and side-chain conformational preferences during peptide assembly. The asymmetrical substitution pattern and protected backbone design make the compound a chiral intermediate and peptide-compatible reagent for studying guanidino chemistry, side-chain sterics, and downstream derivatization routes in synthetic and biochemical workflows.

1. Peptide Synthesis

Fmoc-Arg(Me)2-OH (asymmetrical) serves as a protected arginine side-chain building block for solid-phase peptide synthesis and automated peptide assembly where Fmoc removal followed by amide bond formation is required. The Fmoc-protected α-amine and free α-carboxylic acid configuration align with standard peptide coupling strategies, while the asymmetrically dimethylated guanidino group provides a chemically distinct arginine mimic for incorporating sterically tuned, strongly basic side chains into peptide sequences. The guanidinium-like functionality can participate in salt-bridge formation and multidentate hydrogen bonding within growing chains, supporting realistic evaluation of cationic residue behavior in peptide scaffolds. Downstream peptide products can be used as research-grade materials for side-chain structure-function studies and as intermediates for further functionalization or conjugation.

2. Chemical Biology

Fmoc-Arg(Me)2-OH (asymmetrical) functions in chemical biology workflows that require incorporation of a methylated guanidino residue to probe recognition, binding, and electrostatic interactions in biomolecular contexts. The protected amino acid framework enables site-specific placement into peptides or peptidomimetics, while the asymmetrical dimethyl substitution pattern can alter guanidino protonation microstates, hydrogen-bond geometry, and local conformational sampling relative to canonical arginine. The free carboxyl group and Fmoc-protected nitrogen support controlled coupling to form amide-linked constructs for affinity probes, cell-surface binding reagents, or receptor-binding peptide analogs. Resulting labeled or modified biomolecule fragments can be used to generate mechanistic readouts for guanidino-dependent interactions and to support structure-activity relationship investigations.

3. Peptidomimetics

Fmoc-Arg(Me)2-OH (asymmetrical) is suitable for peptidomimetic construction where guanidino-like side-chain electronics and sterics are engineered to tune binding modes and membrane-associated behavior. The Fmoc-protected α-amino group and carboxylic acid allow conversion into peptide analogs that retain a cationic, hydrogen-bonding motif while introducing asymmetrical methyl groups that can influence rotamer populations and intramolecular ion pairing. The methylated guanidino unit can be carried through as a stable functional handle for subsequent transformations such as side-chain derivatization, conjugation, or incorporation into constrained scaffolds. Peptidomimetic derivatives prepared from this chiral building block can serve as downstream candidates for fragment-based molecular design and SAR studies focused on cationic residue placement.

4. Side-Chain Functionalization

Fmoc-Arg(Me)2-OH (asymmetrical) can be applied as a functionalized amino acid intermediate for side-chain chemistry where the dimethylated guanidino group provides a controlled platform for further derivatization. The asymmetrical methylation pattern affects nucleophilicity, protonation behavior, and steric accessibility of the guanidinium nitrogens, which can be relevant when designing conjugation handles, ion-pairing motifs, or chemically modified cationic residues for downstream synthetic routes. The Fmoc protection strategy supports selective deprotection to expose the α-amine during peptide assembly, while the carboxylic acid enables activation or coupling to generate derivatives that carry the guanidino functionality into larger molecules. Resulting functionalized amino acid and peptide derivatives can be used to build libraries for chemical manufacturing of specialty reagents and for applied research requiring reproducible cationic side-chain presentation.

5. Pharmaceutical Manufacturing

Fmoc-Arg(Me)2-OH (asymmetrical) is relevant to pharmaceutical manufacturing contexts that require reproducible synthesis of protected amino acid building blocks and defined peptide intermediates for process development. The combination of Fmoc-protected α-amino functionality with a free carboxylic acid supports scalable peptide coupling workflows and controlled deprotection steps in manufacturing-scale synthesis of peptide-based intermediates. The asymmetrically dimethylated guanidino side chain provides a chemically specified residue for producing peptide analogs with tailored basicity and hydrogen-bonding characteristics, which can be important for consistent physicochemical properties across synthetic batches. Downstream utilization includes preparation of well-defined peptide fragments for further processing into larger active or investigational structures, as well as generation of process chemistry intermediates used in fine chemical production.

6. Analytical Research

Fmoc-Arg(Me)2-OH (asymmetrical) supports analytical research and method development by enabling preparation of defined peptide standards containing a methylated arginine surrogate. The Fmoc-protected backbone and free carboxylic acid facilitate incorporation into model peptides that present the asymmetrically dimethylated guanidino motif at known positions, supporting chromatographic and mass spectrometric characterization of cationic residue behavior. The guanidino substitution pattern can improve discrimination between arginine variants by altering fragmentation pathways, ionization efficiency, and retention characteristics relative to unmodified arginine-containing peptides. Analytical derivatives generated from this chiral building block can be employed for impurity profiling, identity confirmation, and reference material preparation in amino acid derivative and peptide chemistry workflows.

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