Z-β-D-HomoAla-OH Handling & Application Protocol

Z-β-D-HomoAla-OH is a Cbz (benzyloxycarbonyl)-protected beta-D-homo-alanine derivative widely employed as a chiral building block in solid- and solution-phase peptide synthesis, enabling the incorporation of a homologated D-amino acid residue into peptide or peptidomimetic scaffolds.

Product Name

Z-β-D-HomoAla-OH

SKU

Z727857

Chemical Class

Cbz-protected β-D-homo-amino acid (beta-amino acid derivative)

Primary Application

Peptide synthesis building block; peptidomimetic and medicinal chemistry research

Protecting Group

Z (Cbz, benzyloxycarbonyl) on the amine; free carboxylic acid

Stereochemistry

D-configuration at the beta-carbon

Recommended Storage

Cool, dry, dark conditions; typically 2–8 °C or as specified on the CoA

Overview and Chemical Background

Z-β-D-HomoAla-OH belongs to the class of β-homo-amino acids, which are structural analogues of canonical α-amino acids extended by one methylene unit in the backbone. The Z (Cbz) group on the nitrogen provides orthogonal amine protection compatible with Fmoc and Boc solid-phase peptide synthesis (SPPS) strategies, as it can be removed selectively by hydrogenolysis (H₂/Pd-C) or by strong Lewis acids without affecting standard side-chain protecting groups.

The D-configuration of this building block makes it particularly valuable for the synthesis of D-amino-acid-containing peptides, which are of interest in the development of protease-resistant peptidomimetics, enzyme inhibitor scaffolds, and conformationally constrained analogues of bioactive peptides.

Incorporation of β-homo-amino acids such as β-D-HomoAla into a peptide backbone increases backbone length and flexibility at the modified residue, and can promote specific secondary structures (e.g., 12- or 14-membered hydrogen-bonded rings in β-peptides), making such building blocks important tools in foldamer research.

Storage, Handling, and Safety

Storage: Store Z-β-D-HomoAla-OH under cool (2–8 °C recommended), dry, and dark conditions. Protect from moisture to prevent hydrolytic degradation of the Cbz protecting group. Consult the Certificate of Analysis (CoA) for the exact storage specification supplied with each lot.

Stability: The compound is generally stable as a dry solid under the recommended conditions. Prolonged exposure to strong acids, bases, or reducing conditions should be avoided prior to intentional deprotection.

Handling precautions: Handle in a well-ventilated area or fume hood. Wear appropriate personal protective equipment (PPE) including laboratory coat, chemical-resistant gloves, and safety eyewear. Avoid inhalation of dust. Refer to the Safety Data Sheet (SDS) provided by Aladdin Scientific for comprehensive hazard information before use.

Waste disposal: Dispose of waste material in accordance with local, regional, and national regulations. Do not pour organic reagent waste into the drain without treatment.

Reconstitution and Solubility

Z-β-D-HomoAla-OH contains a free carboxylic acid and a Cbz-protected amine. General solubility guidance for this class of compound is as follows:

• Organic solvents: The compound is typically soluble in polar aprotic solvents such as DMF (N,N-dimethylformamide), DMSO, and dichloromethane (DCM), which are standard media for peptide coupling reactions.
• Aqueous solubility: Limited in pure water; solubility may be enhanced at basic pH (e.g., in dilute NaOH or aqueous sodium bicarbonate) due to carboxylate formation.
• Recommended procedure: Weigh the required amount of compound in a tared vessel under dry conditions. Dissolve in the minimum volume of anhydrous DMF or DMSO. Dilute to the desired concentration with the appropriate reaction solvent. Filter through a 0.2 µm syringe filter if particle-free solutions are required.

Note: Verify solubility empirically for each new lot. Consult the CoA for lot-specific purity data.

Peptide Coupling Protocol

Z-β-D-HomoAla-OH can be incorporated into peptide sequences using standard solution-phase or solid-phase coupling chemistries. The following general protocol applies to amide bond formation using carbodiimide or uronium/phosphonium-type coupling reagents:

1. Prepare the activated ester: Dissolve Z-β-D-HomoAla-OH (1.0–1.5 equiv.) in anhydrous DMF. Add a coupling reagent such as HATU, HBTU, or DIC (1.0–1.5 equiv.) and a base such as DIPEA (2–4 equiv.) or NMM. Stir for 2–5 minutes at room temperature to pre-activate.
2. Coupling: Add the amine component (e.g., resin-bound amine in SPPS, or free amine nucleophile in solution phase; 1.0 equiv.) to the activated solution. React at room temperature for 30–120 minutes with stirring or agitation. Monitor reaction completion by Kaiser test (ninhydrin) for primary amines, or by analytical HPLC/TLC.
3. Washing (SPPS): Drain the resin and wash sequentially with DMF (×3), DCM (×3), and DMF (×3) to remove excess reagents.
4. Workup (solution phase): Dilute the reaction mixture with ethyl acetate. Wash with 5% citric acid, saturated NaHCO₃, and brine. Dry over MgSO₄, filter, and concentrate under reduced pressure.
5. Cbz removal: When required, remove the Cbz protecting group by hydrogenolysis: dissolve the substrate in MeOH or EtOH, add 10% Pd/C (catalytic), and stir under H₂ atmosphere (balloon pressure) for 2–4 hours. Filter through Celite and concentrate. Alternatively, use HBr/AcOH or TMSI for acid-labile deprotection conditions.

Optimize equivalents, solvents, and reaction times based on substrate reactivity and scale. Coupling of β-amino acids may require longer reaction times or more activated reagents compared to α-amino acids.

Quality Control and Troubleshooting

Quality control: Each lot of Z-β-D-HomoAla-OH from Aladdin Scientific is supplied with a Certificate of Analysis (CoA) reporting identity, purity, and appearance. Confirm identity by ¹H NMR, ¹³C NMR, or HRMS prior to use in critical applications. Check optical rotation to verify D-stereochemistry if chiral integrity is essential to the project.

Common issues and troubleshooting:

• Low coupling yield: β-Amino acids are inherently less reactive than α-amino acids in standard coupling reactions due to increased steric bulk and altered pKa. Use more reactive coupling reagents (e.g., HATU with HOAt additive) or extend reaction time. Double coupling is recommended in SPPS.
• Racemization: Minimize base concentration and reaction temperature. Use coupling reagents with low epimerization tendency. Verify stereochemical integrity by chiral HPLC or optical rotation measurement.
• Poor solubility: Switch to a more polar aprotic solvent (DMF preferred). Gentle warming (40–50 °C) may assist dissolution; avoid prolonged heating.
• Incomplete Cbz removal: Ensure adequate H₂ pressure and catalyst loading. Replace Pd/C if catalyst has been stored improperly. Consider TFA-based or HBr/AcOH alternatives if hydrogenolysis is not feasible.

Frequently asked questions

What is Z-β-D-HomoAla-OH used for in peptide synthesis?

Z-β-D-HomoAla-OH serves as a Cbz-protected β-D-homo-alanine building block for the introduction of a homologated D-amino acid residue into peptide or peptidomimetic sequences. It is used in both solid-phase and solution-phase peptide synthesis to create protease-resistant, conformationally constrained, or β-peptide scaffolds for medicinal chemistry and foldamer research.

How should I remove the Cbz (Z) protecting group from the final peptide?

The Cbz group is most commonly removed by catalytic hydrogenolysis: dissolve the substrate in methanol or ethanol, add 10% Pd/C, and stir under a hydrogen atmosphere (balloon pressure) for 2–4 hours at room temperature, then filter through Celite and concentrate. Alternative methods include treatment with HBr in acetic acid or TMSI, which are useful when hydrogenation-sensitive functional groups are present in the molecule.

Why might coupling of Z-β-D-HomoAla-OH be slower than that of a standard α-amino acid?

β-Amino acids have a methylene group inserted between the amino and carboxyl functionalities, which increases steric hindrance around the carboxyl group and alters its electronic properties compared to α-amino acids. This results in reduced intrinsic reactivity in amide bond-forming reactions. To compensate, use highly activated coupling reagents (e.g., HATU/HOAt), longer reaction times, double coupling steps in SPPS, and mild heating if compatible with the substrate.

How should Z-β-D-HomoAla-OH be stored to maintain stability?

Store the compound as a dry solid at 2–8 °C in a tightly sealed container, protected from moisture, light, and strong oxidizing or reducing agents. Avoid repeated freeze-thaw cycles if solutions are prepared. Always consult the Certificate of Analysis (CoA) provided with each specific lot for confirmed storage recommendations.

What analytical methods can confirm the identity and purity of Z-β-D-HomoAla-OH?

Identity can be confirmed by ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry (HRMS). Purity is typically assessed by reverse-phase HPLC (RP-HPLC). Chiral HPLC or optical rotation measurement is recommended to verify the D-stereoconfiguration. Refer to the Aladdin Scientific CoA for lot-specific analytical data.

References

1. Seebach, D.; Beck, A. K.; Bierbaum, D. J. The World of β- and γ-Peptides Comprised of Homologated Proteinogenic Amino Acids and Other Components. Chemistry & Biodiversity 2004, 1 (8), 1111–1239. doi:10.1002/cbdv.200490087
2. Lelais, G.; Seebach, D. β2-amino acids — syntheses, occurrence in natural products, and components of β-peptides. Biopolymers (Peptide Science) 2004, 76 (3), 206–243. doi:10.1002/bip.20088
3. El-Faham, A.; Albericio, F. Peptide Coupling Reagents, More than a Letter Soup. Chemical Reviews 2011, 111 (11), 6557–6602. doi:10.1021/cr100048w

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.