Ac-4,5-dehydro-Leu-OH is an amino acid derivative featuring a leucine backbone bearing a 4,5-dehydro (alkene) modification that alters the side-chain unsaturation while maintaining an amino acid framework. The molecule contains an N-acetyl (Ac-) group on the amino functionality and a free carboxylic acid (-OH), with the double bond in the 4,5-position providing a constrained, more rigid side-chain geometry relevant to peptide and peptidomimetic structure. In synthesis and chemical biology research, this dehydroamino acid is used as a precursor building block for preparing modified peptides and studying how unsaturation and N-acetylation influence conformational behavior, reactivity, and analytical properties.
CAT No: CP27564
CAS No:88547-24-4
Synonyms/Alias:Ac-4,5-dehydro-leu-oh;88547-24-4;Ac-4,5-dehydro-L-leucine;CTK8F7488;ZINC2560821;6071AH;AKOS006274723;KB-47030;FT-0695709;4-Pentenoicacid,2-(acetylamino)-4-methyl-,(S)-(9CI)
Ac-4,5-dehydro-Leu-OH is an N-acetylated, non-proteinogenic leucine analogue bearing a 4,5-dehydro motif in the side chain, providing a constrained alkene functionality while retaining a carboxylic acid for further derivatization. This structural combination makes the compound a useful building block for preparing peptide and peptidomimetic segments where backbone or side-chain unsaturation is used to probe structure, conformational effects, or reactivity. Researchers also leverage the N-terminal acetylation to emulate common peptide termini and improve consistency in downstream coupling and analytical workflows.
1. Peptidomimetic Segment Building
Ac-4,5-dehydro-Leu-OH is used by peptide chemistry groups to assemble peptidomimetic fragments that incorporate a dehydro-leucine residue as a structural probe or conformational modifier. The N-acetylated amino terminus supports workflows where terminal acetylation is desired to match experimentally relevant peptide contexts, while the carboxylic acid enables conversion into coupling-ready derivatives for segment condensation. In practice, this reagent is often selected when the unsaturated side-chain motif is expected to influence local geometry or serve as a defined chemical handle within synthetic peptide analog libraries.
2. Structure-Reactivity Probe Design
Ac-4,5-dehydro-Leu-OH is applied in chemical biology and medicinal chemistry research as a defined unsaturated amino acid analogue for studying how side-chain unsaturation affects chemical reactivity and molecular recognition in peptide-like scaffolds. Teams developing SAR-focused peptidomimetics incorporate this residue to create controlled variations in sterics and electronic character relative to saturated leucine, enabling systematic comparisons across analog series. The N-acetyl group helps standardize terminal context so that observed differences can be attributed more directly to the dehydro functionality rather than to terminal charge or hydrogen-bonding changes.
3. Analytical Reference and Method Development
Ac-4,5-dehydro-Leu-OH is also used as an analytical reference material in LC-MS and related characterization workflows for peptidomimetic synthesis and impurity profiling. Because the compound is a well-defined leucine analogue with a distinct dehydro side chain and an N-acetylated terminus, it can serve as a target compound for method qualification, calibration of fragment standards, and verification of residue incorporation in synthetic batches. Analytical teams often prefer such defined standards when monitoring closely related peptide analogs where conventional amino acid standards do not capture the same retention or mass characteristics.
4. Pharmaceutical Intermediate Derivatization
Ac-4,5-dehydro-Leu-OH functions as a specialized intermediate for downstream derivatization into more complex peptide-building reagents and peptidomimetic intermediates used in pharmaceutical intermediate development. Process and development chemists use the carboxylic acid functionality as a starting point for preparing activated forms or conjugation-ready derivatives, while the dehydro motif provides a chemically distinct structural element that can be carried into later-stage scaffold assembly. This makes the compound relevant in synthetic design efforts where a specific, non-natural leucine-like residue must be introduced with reproducible terminal acetylation.
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