Fmoc Amino Acids¶
TL;DR¶
Fmoc amino acids are the building blocks of SPPS, requiring ≥99% HPLC purity and ≤0.1% D-enantiomer content. Proper storage at -20 °C prevents degradation.
Definition¶
Fmoc (9-fluorenylmethoxycarbonyl) protected amino acids are the primary building blocks for Fmoc-SPPS. The Fmoc group protects the α-amino group during coupling cycles.
Structure¶
- Fmoc-NH-CHR-COOH
- R = side chain (varies by amino acid)
- Side chains may also be protected
Common Fmoc-Amino Acids¶
| Amino Acid | Abbreviation | Side-Chain Protection |
|---|---|---|
| Alanine | Fmoc-Ala-OH | None |
| Arginine | Fmoc-Arg(Pbf)-OH | Pbf |
| Asparagine | Fmoc-Asn(Trt)-OH | Trt |
| Aspartic acid | Fmoc-Asp(OtBu)-OH | tBu |
| Cysteine | Fmoc-Cys(Trt)-OH | Trt |
| Glutamic acid | Fmoc-Glu(OtBu)-OH | tBu |
| Glutamine | Fmoc-Gln(Trt)-OH | Trt |
| Glycine | Fmoc-Gly-OH | None |
| Histidine | Fmoc-His(Trt)-OH | Trt |
| Isoleucine | Fmoc-Ile-OH | None |
| Leucine | Fmoc-Leu-OH | None |
| Lysine | Fmoc-Lys(Boc)-OH | Boc |
| Methionine | Fmoc-Met-OH | None |
| Phenylalanine | Fmoc-Phe-OH | None |
| Proline | Fmoc-Pro-OH | None |
| Serine | Fmoc-Ser(tBu)-OH | tBu |
| Threonine | Fmoc-Thr(tBu)-OH | tBu |
| Tryptophan | Fmoc-Trp(Boc)-OH | Boc |
| Tyrosine | Fmoc-Tyr(tBu)-OH | tBu |
| Valine | Fmoc-Val-OH | None |
What Quality Parameters Define Fmoc Amino Acids?¶
| Parameter | Typical Spec | Method |
|---|---|---|
| Purity (HPLC) | ≥99% | RP-HPLC |
| Optical purity | ≤0.1% D-enantiomer | Chiral HPLC |
| Water content | ≤0.5% | Karl Fischer |
| Residual solvents | ≤0.1% | GC |
| Free amine | ≤0.1% | Kaiser test |
| Appearance | White to off-white powder | Visual |
How Should Fmoc Amino Acids Be Stored?¶
- Temperature: -20 °C
- Moisture: Desiccated (hydroscopic)
- Light: Protected from UV
- Shelf life: 2 years at -20 °C
Application in SPPS¶
- Activator converts Fmoc-AA-OH to active ester
- Active ester couples to free N-terminus on growing peptide
- Piperidine removes Fmoc group after coupling
-
Next Fmoc-AA-OH is added
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Fmoc-Protected Amino Acids for SPPS — Review the section above for key parameters, methods, and quality criteria.
- Common Fmoc-Amino Acids — Review the section above for key parameters, methods, and quality criteria.
- What Quality Parameters Define Fmoc Amino Acids? — See the section for detailed parameters and specifications.
- How Should Fmoc Amino Acids Be Stored? — See the section for detailed parameters and specifications.
🔗 Related: Coupling Reaction | Boc Amino Acids | HBTU | HATU | Custom Peptide Synthesis & OEM
Key Takeaways¶
- Definition — Review the section above for key parameters, methods, and quality criteria.
- Common Fmoc-Amino Acids — Review the section above for key parameters, methods, and quality criteria.
- What Quality Parameters Define Fmoc Amino Acids? — See the section above for detailed parameters and specifications.
- How Should Fmoc Amino Acids Be Stored? — See the section above for detailed parameters and specifications.