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Z-Val-Pro-OH is Cbz-L-Val-L-Pro-OH, a protected dipeptide containing a β-branched valine residue followed by conformationally restricted proline. The C-terminal proline carboxyl group remains free for additional activation and coupling.
Val-Pro is a distinctive short motif because the two residues influence local backbone behavior in different ways. Valine adds steric bulk near the backbone, while proline restricts φ geometry and can support cis/trans peptide-bond isomerization. A preformed fragment carries that specific sequence unit into the next synthetic step.
Product Information
| Product Name | Z-Val-Pro-OH |
| Catalog No. | AS4095 |
| CAS No. | 53331-43-4 |
| Molecular Formula | C18H24N2O5 |
| Molecular Weight | 348.40 g/mol |
| Chemical Identity | Cbz-L-Val-L-Pro-OH |
| Building Block Type | Cbz-protected Val-Pro dipeptide fragment |
| Primary Applications | Protected-fragment synthesis, proline-containing peptide assembly, conformational studies and convergent routes |
Why the Val-Pro Motif Is Structurally Distinct
Proline’s pyrrolidine ring restricts backbone geometry and changes the energetic balance between cis and trans peptide-bond states. In a finished sequence, a Val-Pro motif can influence local turns, folding kinetics and chromatographic behavior. We consider this a useful reason to treat the dipeptide as a defined motif rather than simply as two protected residues.
Proline Isomerization Can Complicate Analytical Interpretation
Cis/trans proline populations can sometimes produce broadened or split chromatographic or NMR signals without a change in covalent mass. This can be mistaken for a chemical impurity if LC-MS, HPLC and conformational behavior are not interpreted together. Our peptide synthesis troubleshooting guide provides additional context for distinguishing synthesis-related impurities from sequence-dependent behavior.
Val-Pro vs Val-Ala
Z-Val-Ala-OH provides a closely related protected fragment in which the C-terminal residue is alanine rather than proline. Comparing Val-Pro and Val-Ala motifs can therefore help separate proline-specific conformational effects from those associated with the N-terminal valine residue.
Why Use a Preassembled Val-Pro Fragment?
The fragment removes one downstream coupling and fixes the Val-Pro sequence before longer assembly. This can be useful in convergent synthesis or in analog series that repeat the same motif. It does not remove later sequence-dependent problems such as hydrophobic aggregation or difficult coupling elsewhere in the chain.
Procurement and QC Considerations
Confirm CAS 53331-43-4, C18H24N2O5, MW 348.40 g/mol and L-Val-L-Pro stereochemistry. Review HPLC purity together with mass and structure information; proline-related conformational behavior can affect chromatographic appearance without indicating a different molecular formula.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
Certificates of Analysis (COAs) are batch-specific. Please contact us to request the COA for your product, and we will provide it by email.
Frequently Asked Questions
Why is proline important in Z-Val-Pro-OH?
Proline constrains local backbone geometry and can support cis/trans peptide-bond isomerization.
How does Z-Val-Pro-OH differ from Z-Val-Ala-OH?
The C-terminal residue is proline instead of alanine, giving the fragment a more constrained local backbone environment.
Can the C-terminal proline carboxyl be extended?
Yes. It remains free and can be activated for further amide-bond formation.
Related Technical Resources
For proline-rich, conformationally constrained or otherwise difficult sequences, see our custom peptide synthesis service.