Fmoc-Dap(Mtt)-OH is an orthogonally protected L-2,3-diaminopropionic acid building block. Fmoc protects the backbone alpha-amino group, while the short side-chain beta-amino group is masked with the acid-labile 4-methyltrityl (Mtt) group.

Its main value is spatial control. Dap places an amine only one carbon from the peptide backbone, so a branch, label or intramolecular linkage introduced through this handle occupies a very different position from the same modification installed on Lys or Orn.

Product Information

Why Dap Is Not a Short Lysine

Dap should not be treated as a smaller interchangeable lysine residue. The beta-amino group is much closer to the peptide backbone, which changes steric accessibility, cyclization geometry and the distance between the main chain and any attached cargo. We consider this most important when the residue is being used as a deliberate architectural element rather than simply as an extra amine.

Fmoc/Mtt Orthogonality in Practice

Standard base-mediated Fmoc removal can be used for chain elongation while Mtt remains on the side-chain nitrogen. Later, controlled mild-acid treatment can expose the beta-amine on resin. Because Mtt selectivity depends on the complete protecting-group set, the broader Fmoc-SPPS workflow should be reviewed before fixing a deprotection sequence.

Branching, Labeling and Cyclization

Once the beta-amine is exposed, it can be acylated with a linker, fluorophore, lipid, chelator or second peptide segment. It can also participate in side-chain lactam formation or other ring-closing strategies. For cyclic designs, the short Dap tether can create ring geometries that are not accessible from Lys or Orn.

Coupling and QC Considerations

The bulky Mtt group can increase steric demand during incorporation. For difficult sequences, we prefer to confirm coupling completion rather than assuming that a standard cycle is sufficient. Lot-specific identity should include CAS, formula, L stereochemistry and the Fmoc/Mtt protection map; LC-MS confirms mass but does not establish enantiomeric identity.

Procurement and QC Considerations

For a project using Dap as a branch point or cyclization handle, the residue should be evaluated together with the complete sequence and modification plan. Alan Scientific can incorporate this chemistry through custom branched, labeled or cyclic peptide synthesis.

Product Documents

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

Fmoc-Dap(Mtt)-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 does Mtt protect?

Mtt protects the Dap side-chain beta-amino group; Fmoc protects the alpha-amino group.

Why choose Dap instead of Lys?

Dap provides a much shorter side-chain amine, changing spacing and cyclization geometry.

Can Mtt be removed on resin?

Yes, with compatible controlled mild-acid conditions selected for the full protecting-group set.

Related Technical Resources

Compare broader noncanonical residue strategies

Browse specialty peptide building blocks

Research Use Only.