Boc-Tyr(tBu)-Aib-OH is a protected Tyr-Aib dipeptide containing tert-butyl protection on the tyrosine phenolic oxygen and an N-terminal Boc group. The second residue is Aib (alpha-aminoisobutyric acid), an alpha,alpha-disubstituted noncanonical amino acid that increases steric demand around peptide-bond formation.

Public chemical records identify CAS 2639221-78-4 for Boc-L-Tyr(tBu)-Aib-OH with molecular formula C22H34N2O6 and molecular weight 422.52 g/mol. Lot-specific identity and analytical specifications should be verified against the accompanying COA.

Product Information

Why the Tyr-Aib Bond Is the Important Part of This Building Block

Aib is substantially more hindered than alanine because the alpha carbon carries two methyl substituents. Forming an amide bond adjacent to Aib can therefore require more aggressive activation, longer reaction time, or repeated coupling than a routine proteinogenic residue. A preformed Tyr-Aib fragment moves that particular bond into the starting material, where identity and purity can be checked before the fragment is used downstream.

Aib Is a Conformational Design Residue

Aib is widely used to restrict local backbone conformational space and can favor helical structure in suitable sequences. Its effect is position- and sequence-dependent. Our overview of noncanonical amino acids in peptide design places Aib in the broader context of using backbone substitution to change stability, conformation and target recognition without implying that a single Aib substitution has a universal biological effect.

Protection Strategy: Boc and Tyr(tBu)

The N-terminal Boc group and the Tyr side-chain tBu ether are both acid-labile, so this fragment fits routes designed around acid-mediated deprotection. It is not a direct substitute for Fmoc-Tyr(tBu)-OH in repetitive Fmoc-SPPS because the N-terminal protection strategy is different. The choice between a preformed Boc-Tyr(tBu)-Aib fragment and stepwise Fmoc chemistry should be made at the route level.

Procurement and QC Considerations

Confirm CAS 2639221-78-4, formula C22H34N2O6, MW 422.52 g/mol, L-Tyr stereochemistry, Aib identity, and the exact Boc/tBu protection map. We also recommend checking HPLC purity and MS together, because deletion or partially deprotected species can affect a later difficult coupling even when the main molecular ion is present.

If the target sequence contains Aib plus other sterically hindered or aggregation-prone residues, peptide synthesis for Aib-containing and other sterically demanding sequences can be reviewed before fixing the final route.

Product Documents

A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.

Boc-Tyr(tBu)-Aib-OH 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 Aib in Boc-Tyr(tBu)-Aib-OH?

Aib is alpha-aminoisobutyric acid, an alpha,alpha-disubstituted noncanonical amino acid used to alter backbone sterics and conformation.

Why use a preformed Tyr-Aib dipeptide?

It places the sterically demanding Tyr-Aib amide bond in a separately characterized starting fragment and removes that coupling from the downstream route.

Is this interchangeable with Fmoc-Tyr(tBu)-OH?

No. This is a Boc-protected dipeptide containing Aib; Fmoc-Tyr(tBu)-OH is a single Fmoc-protected tyrosine building block.

Related Technical Resources

For other protected short fragments, explore specialty peptide building blocks selected for non-routine routes. When difficult coupling is the main concern, the SPPS side-reaction and difficult-coupling guide provides useful route context.

Research Use Only.