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Fmoc-N(Et)-Ala-OH is N-Fmoc-N-ethyl-L-alanine, a noncanonical amino acid designed to introduce backbone N-ethylation at a defined peptide position. The ethyl group is attached to the amino nitrogen, not to the alpha carbon or alanine side chain.
N-alkylated residues are used to alter backbone hydrogen-bonding, sterics and conformational preferences. They belong to the same broader design space described in our noncanonical amino acids in peptide drug discovery, but their synthetic behavior is often more demanding than that of ordinary Fmoc amino acids.
Product Information
| Product Name | Fmoc-N(Et)-Ala-OH |
| Catalog No. | AS2117 |
| CAS No. | 84000-09-9 |
| Molecular Formula | C20H21NO4 |
| Molecular Weight | 339.39 g/mol |
| Chemical Identity | N-Fmoc-N-ethyl-L-alanine |
| Building Block Type | Fmoc-protected backbone N-ethyl amino acid |
| Primary Applications | Backbone N-alkylated peptide synthesis, peptide SAR and conformational/permeability studies |
What N-Ethylation Changes in the Final Peptide
After incorporation and Fmoc removal, the residue contributes a tertiary amide at the preceding peptide bond and removes one backbone N-H hydrogen-bond donor. The larger ethyl substituent also increases local steric demand. These changes can affect conformation, proteolysis, permeability and target binding, but the direction of the effect is sequence-dependent.
Why Coupling Can Be Difficult
N-alkyl amino acids are less nucleophilic and more sterically hindered during chain extension. The residue after N-ethyl alanine can therefore require stronger activation, longer coupling or repeat coupling. We recommend monitoring completion instead of simply carrying a standard cycle forward, because deletion products from a difficult N-alkyl coupling can persist into the final purification.
N-Ethyl Is Not Alpha-Ethyl
The product name must be read literally: N(Et) refers to substitution on nitrogen. It is not an alpha-ethyl alanine analog. For laboratories selecting other nonstandard Fmoc monomers, our SPPS guide for Fmoc protection and coupling strategy provides a broader framework for protection, sterics and route compatibility.
Procurement and QC Considerations
Confirm CAS 84000-09-9, formula C20H21NO4, MW 339.39 g/mol and L-alanine stereochemistry. LC-MS verifies mass but does not by itself confirm stereochemical identity or distinguish every positional isomer. Public SDS information classifies the material as harmful if swallowed and as a skin, eye and respiratory irritant.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
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
Where is the ethyl group in Fmoc-N(Et)-Ala-OH?
It is attached to the amino nitrogen, creating an N-ethylated alanine building block.
Why use N-ethylation in a peptide?
It can change backbone hydrogen bonding, steric environment, conformation, protease recognition and permeability.
Does N-ethyl alanine couple like standard alanine?
Often not. N-alkylated residues can be more sterically demanding and may require more aggressive or repeated coupling conditions.
Related Technical Resources
Read about noncanonical residues and peptide property engineering.
Discuss synthesis of an N-alkylated custom peptide.