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Fmoc-2,3,4,5,6-pentafluoro-L-phenylalanine (Fmoc-Phe(F5)-OH; CAS 205526-32-5) is an Fmoc-protected L-phenylalanine derivative with a defined fluorine pattern on the aromatic ring. It enables direct installation of the modified phenylalanine residue during Fmoc-SPPS for peptide SAR, medicinal chemistry, and noncanonical residue studies.
The 2,3,4,5,6 substitution pattern changes the electronic and steric environment of the phenyl side chain while preserving the alpha-amino-acid framework. Because positional isomers can behave differently in a peptide, the ring substitution pattern should be treated as a primary identity attribute.
Product Information
| Product Name | Fmoc-2,3,4,5,6-pentafluoro-L-phenylalanine |
| Preferred Short Name | Fmoc-Phe(F5)-OH |
| Catalog No. | AS102 |
| CAS No. | 205526-32-5 |
| Molecular Formula | C24H16F5NO4 |
| Molecular Weight | 477.39 g/mol |
| Stereochemistry | L |
| Modification | 2,3,4,5,6 |
| Primary Research Use | Fmoc-SPPS and noncanonical peptide SAR research |
What the 2,3,4,5,6 Substitution Pattern Changes
Fluorine and heavier halogens can alter local polarity, aryl electronics, lipophilicity, and steric surface. These effects can be useful for systematic SAR comparisons, but they do not guarantee improved potency, stability, or solubility in every sequence.
Other position-defined aromatic analogs are available in the position-defined Fmoc residues.
Incorporation During Fmoc-SPPS
The building block is intended for standard Fmoc-based chain assembly. Coupling efficiency should be evaluated in the actual sequence context, since steric crowding near a highly substituted aromatic side chain can become more important in difficult peptide regions.
For general chain-assembly decisions, see our solid-phase synthesis workflow.
Identity, Chirality, and Lot Documentation
When ordering Fmoc-2,3,4,5,6-pentafluoro-L-phenylalanine, verify the exact 2,3,4,5,6 ring substitution, L configuration, molecular formula, and CAS number where assigned. Similar fluorinated phenylalanines can share the same nominal molecular weight but are not interchangeable positional isomers.
A lot-specific COA and analytical purity data are more informative than a generic purity statement. If enantiomeric purity affects the experiment, request stereochemistry-supporting documentation rather than relying on LC-MS identity alone.
Product Documents
MSDS - Fmoc-2,3,4,5,6-pentafluoro-L-phenylalanine (AS102)
The Safety Data Sheet provides product identification, hazard information, handling and storage guidance, exposure controls, transport information, and regulatory information for laboratory use.
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
What does Fmoc-Phe(F5)-OH identify?
It identifies the Fmoc-protected L-configured amino-acid building block with the defined 2,3,4,5,6 aromatic substitution pattern.
Can a positional isomer be substituted if the molecular weight is the same?
No. Positional isomers are distinct chemical entities and can produce different peptide properties even when their formulas and nominal molecular weights are identical.
Does fluorination or halogenation guarantee better peptide activity?
No. These substitutions are controlled SAR variables. Their effects on affinity, conformation, solubility, stability, and activity depend on the complete peptide and assay context.