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Fmoc-Aib-Aib-Aib-OH is a preassembled tripeptide containing three consecutive Aib residues. Aib is α-aminoisobutyric acid, an α,α-disubstituted amino acid widely used to reduce backbone flexibility and favor compact helical conformations.
A related fragment, Boc-Tyr(tBu)-Aib-Aib-OH, combines two Aib residues with a protected Tyr terminus. The two products serve different sequence and protection strategies.
Product Information
| Product Name | Fmoc-Aib-Aib-Aib-OH |
| Catalog No. | AS4188 |
| CAS No. | 889133-42-0 |
| Molecular Formula | C27H33N3O6 |
| Molecular Weight | 495.58 g/mol |
| Building Block Type | Fmoc-protected Aib-Aib-Aib tripeptide fragment |
| Primary Applications | Aib-rich peptide assembly; conformationally constrained peptide synthesis; helical motif construction; fragment coupling |
Three Consecutive Aib Residues Create Strong Conformational Bias
Each Aib residue is sterically substituted at the α-carbon. A tri-Aib segment is therefore far less conformationally permissive than a Gly- or Ala-rich segment and can be used deliberately in helix- or turn-focused peptide design.
The Fragment Avoids Three Stepwise Hindered Installations
Repeated coupling of Aib can be difficult because of α,α-disubstitution. A preassembled tri-Aib fragment can shift that challenge upstream into a characterized reagent and reduce the number of hindered downstream coupling steps.
The C-Terminal Acid Remains the Coupling Handle
The N-terminus is Fmoc-protected and the C-terminal Aib carboxyl is free. Fragment coupling still needs to account for steric hindrance at the terminal Aib junction.
Procurement and QC
Confirm CAS 889133-42-0, C27H33N3O6, MW 495.58 g/mol, exact Aib-Aib-Aib sequence, N-terminal Fmoc, and free terminal carboxyl.
For Aib-rich targets, direct SPPS versus fragment assembly can be compared within the SPPS practical guide and the target sequence.
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
What is Aib?
Aib is α-aminoisobutyric acid, an α,α-disubstituted noncanonical amino acid.
Why use a tri-Aib fragment?
It can avoid multiple downstream formation of highly hindered Aib-containing peptide bonds.
Does a tri-Aib segment guarantee a specific final peptide structure?
No. It creates strong conformational bias, but the complete peptide and environment determine the observed structure.
Related Technical Resources
Discuss Aib-rich custom peptide synthesis