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Fmoc-5-bromo-7-fluoro-L-tryptophan (Fmoc-Trp(5-Br,7-F)-OH; CAS 3012560-69-6) is an Fmoc-protected L-tryptophan derivative carrying the defined 5-Br,7-F mixed-halogen pattern on the indole ring. It is a specialty building block for Fmoc-SPPS and position-specific peptide SAR studies.
The combination of fluorine with chlorine or bromine creates a larger aromatic perturbation than monofluorination alone. It may also provide a synthetic handle in suitably designed downstream chemistry, but any post-assembly transformation must be validated against the peptide sequence, protecting groups, and reaction conditions.
Product Information
| Product Name | Fmoc-5-bromo-7-fluoro-L-tryptophan |
| Preferred Short Name | Fmoc-Trp(5-Br,7-F)-OH |
| Catalog No. | AS108 |
| CAS No. | 3012560-69-6 |
| Molecular Formula | C26H20BrFN2O4 |
| Molecular Weight | 523.36 g/mol |
| Stereochemistry | L |
| Modification | 5-Br,7-F |
| Primary Research Use | Fmoc-SPPS and noncanonical peptide SAR research |
Why the 5-Br,7-F Pattern Requires Exact Identification
Mixed-halogen tryptophans are positional isomers with distinct steric and electronic surfaces. Exact halogen location is therefore essential when interpreting binding or conformational differences between peptide analogs.
Position-defined alternatives are grouped in our halogenated amino acid range.
Use in Peptide Synthesis
The Fmoc-protected alpha-amino group allows incorporation during standard Fmoc-SPPS. Because these residues are bulkier than unmodified tryptophan, difficult sequence contexts may benefit from monitoring coupling completion and adjusting activation or coupling time rather than increasing reagent excess blindly.
The Fmoc peptide assembly provides broader context for difficult coupling and resin-bound aggregation.
Lot Qualification and Procurement
Confirm the full positional name, L stereochemistry, formula, and CAS number where assigned. A generic description such as halogenated tryptophan is insufficient for controlled SAR work.
When the halogen pattern is being used as a medicinal-chemistry probe, lot-specific HPLC/MS data and stereochemical documentation provide stronger identity support than molecular weight alone.
Product Documents
MSDS - Fmoc-5-bromo-7-fluoro-L-tryptophan (AS108)
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-Trp(5-Br,7-F)-OH identify?
It identifies the Fmoc-protected L-configured amino-acid building block with the defined 5-Br,7-F 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.