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Fmoc-L-3,3-Diphenylalanine is a bulky aromatic noncanonical amino acid in which the beta carbon carries two phenyl groups. It is also indexed as Fmoc-beta-phenyl-Phe-OH or Fmoc-Dip-OH. The alpha-amino group is protected with Fmoc and the carboxylic acid remains available for peptide coupling.
The second phenyl ring substantially increases side-chain volume and hydrophobic surface compared with ordinary phenylalanine. This makes the residue useful as a deliberate SAR perturbation when a program needs to test aromatic packing, steric occupancy or hydrophobic binding-pocket tolerance.
Product Information
| Product Name | Fmoc-L-3,3-Diphenylalanine |
| Catalog No. | AS2104 |
| CAS No. | 201484-50-6 |
| Molecular Formula | C30H25NO4 |
| Molecular Weight | 463.52 g/mol |
| Chemical Identity | N-Fmoc-3,3-diphenyl-L-alanine; Fmoc-beta-phenyl-Phe-OH; Fmoc-Dip-OH |
| Building Block Type | Fmoc-protected bulky aromatic noncanonical amino acid |
| Primary Applications | Peptide SAR, aromatic side-chain substitution, conformational studies, peptidomimetic synthesis and medicinal chemistry |
Diphenylalanine Is Not Just “More Phenylalanine”
Adding a second phenyl group changes side-chain geometry and can alter local conformational preferences as well as solubility. The effect on affinity, protease sensitivity or structure is target-dependent. Our overview of noncanonical amino acids in peptide discovery explains why these substitutions are most informative when compared with matched parent sequences rather than interpreted in isolation.
Coupling and Aggregation Can Become More Difficult
The bulky, highly hydrophobic side chain can increase steric demand during coupling and can contribute to poor resin-phase solvation as the sequence grows. We consider double coupling or stronger activation a sequence-specific decision, not a default rule. The guide to aggregation, incomplete coupling and other SPPS failure modes is a useful reference when a Dip-containing peptide develops deletion impurities.
Aromatic Building-Block Selection
Researchers comparing conventional Phe, substituted Phe analogs and larger aromatic residues can browse Alan's phenylalanine and tryptophan building blocks. Fmoc-L-3,3-Diphenylalanine is best positioned as a high-bulk noncanonical option within that design space.
Procurement and QC Considerations
Confirm CAS 201484-50-6, formula C30H25NO4, MW 463.52 g/mol and L configuration. Enantiomers share the same molecular mass, so mass spectrometry does not establish stereochemistry. Lot-specific HPLC, structural identity and stereochemical documentation should be reviewed together.
For synthesis of hydrophobic or bulky-aromatic peptide analogs, custom peptide synthesis with noncanonical aromatic residues can be evaluated together with solubility and purification requirements.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
Fmoc-L-3,3-Diphenylalanine MSDS
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 is Fmoc-L-3,3-Diphenylalanine used for?
It is used to introduce a bulky diphenyl-substituted aromatic residue into peptides for SAR, peptidomimetic and conformational studies.
How does it differ from Fmoc-Phe-OH?
It carries an additional phenyl substituent at the beta carbon, increasing side-chain size and hydrophobicity.
Can LC-MS confirm the L configuration?
No. Enantiomers have the same mass, so stereochemical identity requires structure-specific or chiral documentation.
Related Technical Resources
For other high-information substitutions, explore unusual amino acids and analogs. The specialty peptide building-block collection includes preassembled fragments and additional non-routine scaffolds.