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| Product Name | Fmoc-Thr(tBu)-OH |
|---|---|
| Synonyms | Fmoc-O-tert-butyl-L-threonine |
| Catalog No. | AS0707 |
| CAS Number | 71989-35-0 |
| Molecular Formula | C23H27NO5 |
| Molecular Weight | 397.46 g/mol |
| Appearance | White powder |
| Melting Point | 125–135°C |
| Specific Rotation | +16° ± 2° (C=1 in EtOAc) |
| Storage Temperature | Cool, dry place (≤25°C) |
| Side-Chain Protection | tert-Butyl-protected hydroxyl |
| Primary Application | Fmoc-SPPS |
Product Overview
Fmoc-Thr(tBu)-OH is the standard tBu-protected L-threonine derivative used in Fmoc-SPPS.
Like serine, threonine contains a hydroxyl group requiring protection during conventional peptide synthesis. Unlike serine, threonine is also β-branched, increasing steric congestion around the peptide backbone.
Applications in Peptide Synthesis
| Application | Role of Fmoc-Thr(tBu)-OH |
|---|---|
| Fmoc-SPPS | Standard protected L-threonine building block |
| Thr-Containing Peptides | Protects the hydroxyl during elongation |
| β-Branched Sequences | Introduces a conformationally influential side chain |
| Peptide Libraries | Standard proteinogenic building block |
| SAR Studies | Enables study of hydroxyl + methyl substitution |
| Modified Peptides | Used in sequences later requiring Thr-dependent functionality |
Fmoc-Thr(tBu)-OH in Fmoc-SPPS
The side-chain OH remains tBu-protected during repeated base-mediated Fmoc removal.
During final TFA cleavage, the tBu group is removed to regenerate native threonine.
Why Thr Can Be More Difficult Than Ser
Threonine is β-branched, meaning a methyl substituent sits close to the peptide backbone.
This produces greater steric congestion than serine.
Consequently, difficult Thr coupling steps may require:
longer coupling
double coupling
optimized reagent equivalents
improved resin solvation
stronger coupling chemistry where appropriate
The difficulty becomes more pronounced when Thr is adjacent to another sterically hindered residue.
Threonine Stereochemistry Matters
Threonine contains two stereogenic centers.
This means stereochemical quality involves more than simply distinguishing an L-residue from a D-residue; the allo-threonine configuration is also chemically distinct.
For high-purity peptide synthesis, correct starting-material stereochemistry is therefore particularly important.
Phosphorylation and Glycosylation Projects
Native threonine is a major site for biological phosphorylation and O-linked glycosylation.
Fmoc-Thr(tBu)-OH is appropriate when the goal is ordinary Thr after cleavage.
If the final peptide requires a specifically phosphorylated or glycosylated threonine, another protected derivative or dedicated modification strategy may be required.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
📎 MSDS_Fmoc-Thr(tBu)-OH_AS0707.pdf
Related Technical Resources
Browse Standard Fmoc-Amino Acids.
Read Choosing Fmoc-Protected Amino Acids for Peptide Synthesis.
For difficult or modified sequences, visit Custom Peptide Synthesis.
Why Source Peptide Building Blocks from Alan Scientific?
Alan Scientific supplies protected amino acids and specialized derivatives for conventional Fmoc-SPPS and complex peptide synthesis workflows.
Research Use Only