Fmoc-D-allo-Thr-OH

Fmoc-D-allo-Thr-OH is an Fmoc-protected D-allothreonine amino acid bearing a side-chain hydroxyl group and a stereodefined chiral center at the α-position. The molecule combines an N-fluorenylmethoxycarbonyl (Fmoc) carbamate with a free carboxylic acid, enabling orthogonal handling during protected amino acid synthesis and stepwise peptide assembly. The D-configuration and the allo relationship at the side chain place the hydroxyl-bearing substituent in a distinct stereochemical environment relative to L-threonine, which can influence conformational preferences and hydrogen-bonding patterns in peptide analogs. The unprotected carboxyl group and the side-chain alcohol support controlled derivatization, coupling chemistry, and downstream functional group transformation while remaining compatible with standard Fmoc/tBu peptide synthesis strategies.

1. Peptide Synthesis

Fmoc-D-allo-Thr-OH is used in peptide building block preparation for Fmoc-based solid-phase peptide synthesis where the Fmoc carbamate enables base-mediated N-deprotection and the free carboxylic acid supports amide bond formation. The side-chain hydroxyl on the allothreonine scaffold can participate in hydrogen bonding within growing sequences and can be selectively protected or modified depending on the coupling plan. D-stereochemistry at the α-carbon allows incorporation of stereochemically defined residues for studying sequence stereochemical effects, epimerization sensitivity, and conformational outcomes in peptide libraries. The resulting peptides can be used as research reagents for structure-activity relationship studies and as defined intermediates for further chemical modification.

2. Side-Chain Functionalization

Fmoc-D-allo-Thr-OH is applied in amino acid derivatization workflows that target side-chain hydroxyl chemistry, including conversion to activated esters, ether formation, or protected hydroxyl intermediates for later deprotection. The stereodefined allo-threonine alcohol provides a handle for installing polar, sterically tuned, or labeling-compatible substituents while maintaining the Fmoc-protected amine for controlled coupling or sequential synthesis. The free carboxyl group can be used to generate peptide-ready derivatives or to prepare intermediates for downstream esterification and conjugation chemistry. The ability to tune side-chain functionality supports generation of peptidomimetic analogs and chemically defined fragments used in biochemical research and synthetic organic chemistry.

3. Chiral Building Block Development

Fmoc-D-allo-Thr-OH serves as a chiral amino acid intermediate for stereoselective synthesis routes that require D-configured threonine analogs rather than L stereochemistry. The combination of a stable Fmoc-protected nitrogen and a stereogenic α-carbon allows incorporation into larger chiral frameworks while minimizing racemization during protected amino acid synthesis. The allo side-chain arrangement provides an additional stereochemical distinction that can be leveraged in chiral molecular design, including fragment construction for stereochemically constrained scaffolds. Downstream products include stereodefined peptide analogs, chiral auxiliaries, and intermediate inputs for asymmetric or stereocontrolled manufacturing steps where stereochemical fidelity is required.

4. Chemical Biology Probes

Fmoc-D-allo-Thr-OH is suitable for chemical biology research where hydroxyl-bearing amino acid residues are incorporated into peptides or peptide-like probes that undergo selective post-assembly functionalization. The side-chain alcohol can be transformed into conjugation-ready moieties for attachment of tags, affinity handles, or linkers while the Fmoc group supports reliable peptide coupling during probe construction. D-allothreonine stereochemistry can be used to probe stereochemical recognition, protease tolerance, or binding-site stereoelectronic preferences in biochemical assays without relying on endogenous L-residue incorporation. The resulting labeled or derivatized biomolecular probes can function as defined reagents for molecular recognition studies and mechanistic investigations.

5. Pharmaceutical Intermediate Preparation

Fmoc-D-allo-Thr-OH is employed as a protected amino acid intermediate in industrial fine chemical synthesis of peptide-based intermediates and peptidomimetic fragments used in manufacturing-oriented synthesis planning. The Fmoc-protected amine and free carboxylic acid support scalable peptide coupling chemistry and enable orthogonal protection strategies for hydroxyl handling during multi-step assembly. The stereochemically defined D-allo configuration helps ensure that downstream intermediates maintain the intended stereochemical pattern when incorporated into larger drug-like scaffolds or process intermediates. The compound can therefore be integrated into process chemistry intermediate preparation for controlled generation of well-defined peptide derivatives and chemically characterized building blocks.

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