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| Product Name | Fmoc-Val-OH |
|---|---|
| Synonyms | Nα-Fmoc-L-valine; Fmoc-L-valine |
| Catalog No. | AS0825 |
| CAS Number | 68858-20-8 |
| Molecular Formula | C20H21NO4 |
| Molecular Weight | 339.39 g/mol |
| Appearance | White powder |
| Melting Point | 140–155°C |
| Specific Rotation | -16.5° ± 2° (C=1 in DMF) |
| Storage Temperature | Cool, dry place (≤25°C) |
| Side-Chain Protection | None required |
| Primary Application | Fmoc-SPPS |
Product Overview
Fmoc-Val-OH is the Fmoc-protected form of L-valine and a standard building block for Fmoc-SPPS.
Valine has a hydrophobic β-branched isopropyl side chain and requires no additional side-chain protection.
Although its protecting-group chemistry is straightforward, β-branching makes valine more sterically demanding than residues such as Ala or Gly.
Applications in Peptide Synthesis
| Application | Role of Fmoc-Val-OH |
|---|---|
| Fmoc-SPPS | Standard building block for L-valine |
| Hydrophobic Peptides | Introduces a β-branched nonpolar side chain |
| SAR Studies | Useful for altering hydrophobic packing |
| Peptide Libraries | Standard proteinogenic amino acid |
| Structure Optimization | Can influence local conformational preferences |
| Custom Peptides | Used in linear, cyclic and modified sequences |
Fmoc-Val-OH in Fmoc-SPPS
The free α-carboxyl group is activated for coupling and the Fmoc protecting group is subsequently removed under basic conditions.
No side-chain deprotection is required.
Why Valine Coupling Can Become Difficult
Valine is β-branched.
The additional substitution close to the peptide backbone increases steric hindrance and can slow coupling, particularly when:
the incoming residue is sterically hindered
the resin-bound N-terminal residue is also β-branched
the sequence is strongly hydrophobic
resin swelling is poor
aggregation has already developed
Incomplete coupling can generate a Val deletion sequence, which becomes increasingly difficult to separate as the peptide grows.
β-Branched Residues and Hydrophobic Aggregation
Val, Ile and Thr share β-branching, but Val and Ile additionally contribute substantial hydrophobicity.
In Val-rich or hydrophobic peptide sequences, two effects can therefore operate simultaneously:
steric hindrance + aggregation of the growing peptide chain.
Increasing coupling reagent strength alone may not completely solve a problem caused by poor peptide/resin solvation.
Alan Scientific practical view: when a difficult Val coupling repeatedly fails, the synthesis strategy should address both reaction kinetics and the physical state of the resin-bound peptide.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
Related Technical Resources
Explore Standard Fmoc-Amino Acids.
Read Amino Acids & Peptide Building Blocks.
For difficult β-branched and hydrophobic sequences, see Custom Peptide Synthesis.
Why Source Peptide Building Blocks from Alan Scientific?
Alan Scientific supplies standard Fmoc amino acids and specialized peptide building blocks for research-scale peptide synthesis.
Research Use Only