Fmoc-alpha-Me-L-Asp(tBu)-OH is an Fmoc-protected, α-methylated derivative of the amino acid class Aspartic acid, featuring a side-chain carboxylic acid masked as a tert-butyl ester and an L-stereochemical designation at the α-carbon. The molecule contains an Fmoc carbamate on the amino functionality, a free carboxyl group at the α-position, and a tertiary-butyl ester protecting group on the side-chain carboxylate, with the α-methyl substituent creating a substituted amino acid backbone for peptide incorporation. In peptide synthesis workflows, this protected analogue functions as a building block that supports chemoselective coupling at the α-carboxyl and amino termini while the side-chain carboxyl protection helps control side reactions during stepwise assembly and subsequent deprotection steps.
CAT No: CP25143
CAS No:1072845-47-6
Synonyms/Alias:(S)-Fmoc-alpha-Methylaspartic acid-4-t-butyl ester
Chemical Name:(S)-N-alpha-(9-Fluorenylmethyloxycarbonyl)-C-alpha-methyl-aspartic acid beta-butyl ester (contains 10% MTBE)
Fmoc-alpha-Me-L-Asp(tBu)-OH is an Fmoc-protected, chiral amino acid derivative built on an L-aspartic acid framework bearing a side-chain tert-butyl ester (Asp(tBu)) and an alpha-methyl substitution (alpha-Me). The molecule contains an N-(9-fluorenylmethoxycarbonyl) carbamate that supports controlled peptide coupling after deprotection, alongside a carboxylic acid functionality and a sterically shielded side-chain ester that can be selectively removed or transformed during peptide assembly. The alpha-methyl stereocenter and the L-configuration of the amino acid core provide stereochemical constraint that can influence backbone conformation and subsequent amide bond formation. The combination of protected amine, protected side-chain carboxyl group, and defined stereochemistry makes the compound a practical chiral intermediate for protected amino acid synthesis and peptide building block preparation.
1. Peptide Synthesis
Fmoc-alpha-Me-L-Asp(tBu)-OH serves as a protected amino acid building block for solid-phase peptide synthesis and solution-phase peptide coupling, where the Fmoc carbamate enables orthogonal N-deprotection prior to amide bond formation. The alpha-methyl substitution and the L-aspartate stereochemistry can be used to tune local steric and conformational effects around the Asp residue, while the Asp(tBu) side-chain ester protects the β-carboxyl group from undesired crosslinking or side reactions during chain assembly. The free carboxylic acid and protected amine arrangement supports standard peptide coupling workflows after Fmoc removal, enabling incorporation of an alpha-methylated Asp motif into peptide sequences. Downstream, the tert-butyl ester can be deprotected to furnish a reactive side-chain carboxyl group for further derivatization or native-like peptide chemistry.
2. Peptidomimetics And SAR
Fmoc-alpha-Me-L-Asp(tBu)-OH supports peptidomimetic construction in medicinal chemistry workflows focused on structure-activity relationship studies and backbone modification strategies. The alpha-methylated amino acid core introduces a constrained peptide backbone element that can modulate hydrogen-bonding patterns and reduce conformational flexibility relative to unmodified Asp residues. The protected β-carboxyl group (Asp(tBu)) allows controlled presentation of the side-chain functionality during synthesis, enabling later conversion to carboxylate-bearing analogs or side-chain-modified derivatives for SAR library generation. The Fmoc-protected format also facilitates rapid assembly of analog series where stereochemistry and side-chain identity are maintained across iterative design cycles.
3. Side-Chain Functionalization
Fmoc-alpha-Me-L-Asp(tBu)-OH is suitable for side-chain functionalization routes that require orthogonal protection of the aspartate β-carboxyl group during synthetic elaboration. The tert-butyl ester protection strategy permits selective deprotection under conditions compatible with many peptide and amide-forming chemistries, generating a carboxylate handle for subsequent transformations such as amide formation, ester exchange, or coupling to linkers. The alpha-methyl stereocenter provides a defined chiral environment adjacent to the backbone, which can be leveraged when preparing stereochemically consistent derivatives for chemical biology probes or analytical standards. The resulting functionalized products can be used to generate downstream conjugates, tagged peptides, or carboxylate-functional intermediates for further organic synthesis.
4. Protein Engineering
Fmoc-alpha-Me-L-Asp(tBu)-OH can be employed in protein engineering and recombinant protein modification programs that rely on chemically synthesized peptide segments or semi-synthetic constructs. The Fmoc-protected amino acid format enables incorporation into peptide fragments bearing defined stereochemistry, while the Asp(tBu) protection strategy helps preserve side-chain integrity during fragment assembly and ligation-ready preparation. The alpha-methyl substitution can be used to introduce steric and conformational constraints at Asp positions that may affect local structure, binding interfaces, or proteolytic stability in engineered constructs. The protected side-chain carboxyl group can be unmasked after assembly to enable coupling to additional functional moieties used in protein mapping, scaffold stabilization, or controlled labeling workflows.
5. Pharmaceutical Intermediate Preparation
Fmoc-alpha-Me-L-Asp(tBu)-OH aligns with pharmaceutical intermediate preparation and fine chemical synthesis needs where protected amino acid derivatives serve as controlled inputs for downstream drug-like scaffold construction. The presence of an Fmoc-protected N-terminus and a tert-butyl-protected side-chain carboxyl group supports manufacturing-oriented protection/deprotection logic, allowing isolation of a stable, chiral intermediate that can be converted into carboxylate-bearing derivatives when required. The defined stereochemistry at the alpha position and the L-aspartate configuration help maintain structural fidelity during iterative synthesis of peptide-based or peptidomimetic intermediates. The compound's protected functional group pattern can be integrated into process chemistry routes that prepare sequence-defined building blocks, linker-bearing fragments, or intermediate materials for subsequent coupling steps in specialty chemical production.
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