Fmoc-4-fluoro-L-tryptophan (Fmoc-Trp(4-F)-OH; CAS 2244532-65-6) is an Fmoc-protected L-tryptophan analog carrying fluorine at the indole 4-position. It is used to introduce a position-defined fluorotryptophan residue in Fmoc-SPPS for peptide SAR, aromatic-contact mapping, and noncanonical residue studies.

The L configuration preserves the conventional alpha-amino-acid stereochemistry while introducing a defined indole-ring fluorine. Fluorine substitution provides a compact electronic perturbation of the indole side chain, but its effect on binding, conformation, fluorescence behavior, or metabolic stability depends on the surrounding sequence and assay system.

Product Information

Why Indole 4-Fluorination Is a Distinct SAR Variable

Changing the fluorine from one indole position to another alters the local electrostatic surface without changing the elemental composition of the peptide backbone. The 4-fluoro analog should therefore be compared as a defined positional isomer rather than grouped generically with all fluorotryptophans.

Our position-defined Fmoc residues includes multiple fluorotryptophan positions for matched-residue comparisons.

Fmoc-SPPS Use and Sequence Context

The alpha-amino Fmoc group supports standard base-mediated deprotection and coupling cycles. The indole N-H remains part of the residue, so sequence-specific protection strategy and final cleavage conditions should be considered together with the complete peptide design.

General coupling and deprotection considerations are summarized in our solid-phase synthesis workflow.

Stereochemical and Analytical Selection

For L-tryptophan derivatives, chirality is part of the experimental variable. Formula and MS data can verify mass but cannot by themselves distinguish the D and L enantiomers. Lot-specific chiral purity or equivalent stereochemical documentation is therefore valuable when enantiomeric identity is critical.

For comparative SAR experiments, use the exact positional isomer consistently across synthesis lots and record the lot-specific purity method. Closely related fluoro-tryptophan building blocks should not be substituted solely because they share the same formula and molecular weight.

Product Documents

MSDS - Fmoc-4-fluoro-L-tryptophan (AS107)

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(4-F)-OH identify?

It identifies the Fmoc-protected L-configured amino-acid building block with the defined 4 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.

Research Use Only.