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Fmoc-D-Dap(Mtt)-OH is an orthogonally protected D-2,3-diaminopropionic acid building block. The α-amino group is Fmoc-protected for standard base-mediated elongation cycles, while the short β-amino side chain is protected with 4-methyltrityl (Mtt), allowing selective side-chain exposure under relatively mild acidic conditions.
This architecture makes Dap useful when a peptide needs a branch point, side-chain label, acyl group or cyclization handle positioned closer to the backbone than a lysine side chain would allow.
Product Information
| Product Name | Fmoc-D-Dap(Mtt)-OH |
| Catalog No. | AS2122 |
| CAS No. | 1263046-35-0 |
| Molecular Formula | C38H34N2O4 |
| Molecular Weight | 582.69 g/mol |
| Chemical Identity | Nα-Fmoc-Nβ-Mtt-D-2,3-diaminopropionic acid |
| Building Block Type | Orthogonally protected D-diaminopropionic acid |
| Primary Applications | On-resin side-chain modification, branching, labeling, lactam cyclization and noncanonical peptide synthesis |
Dap Positions the Side-Chain Amine Close to the Backbone
Dap has only one carbon between the α-carbon and the β-amino group. Lysine has a much longer four-methylene side chain. The shorter Dap geometry can substantially change the spacing of an attached label, acyl group or cyclization partner. This is why Dap cannot be treated simply as “short lysine.”
Mtt Enables Selective On-Resin Chemistry
Mtt can often be removed with repeated mild-acid treatments while many other protecting groups remain in place. Once exposed, the β-amino group can be acylated or used as a branching site before global cleavage. Exact selectivity depends on the full protecting-group set, so the sequence should be evaluated as a system rather than by the Mtt group alone.
Branching, Labeling and Cyclization
The exposed Dap side-chain amine can be functionalized with linkers, fatty acids, fluorophores, chelators or another peptide segment. It can also participate in side-chain lactam formation. Our peptide cyclization strategies guide provides context for how side-chain cyclization differs from head-to-tail and disulfide approaches.
D Stereochemistry Is Independent of the Protection Pattern
This SKU is the D enantiomer. The L and D forms have the same formula and nominal mass, so LC-MS alone cannot establish configuration. When Dap is being used to control turn geometry, protease recognition or cyclization topology, stereochemical documentation is essential. The broader role of D and other unusual residues is covered in our noncanonical amino-acid design overview.
Procurement and QC Considerations
Confirm CAS 1263046-35-0, C38H34N2O4, MW 582.69 g/mol, D configuration and the Nα-Fmoc/Nβ-Mtt protection map. For orthogonally protected diamino acids, we recommend reviewing lot-specific HPLC and mass data together with stereochemical documentation and storage history.
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
Why use Dap instead of lysine as a branch point?
Dap places the side-chain amine much closer to the peptide backbone, which changes geometry and steric accessibility.
What does the Mtt group enable?
It allows selective side-chain deprotection under relatively mild acidic conditions so that the β-amino group can be modified on resin.
Can LC-MS distinguish D-Dap from L-Dap?
No. They have the same molecular mass; stereochemical identity requires structure-specific documentation or chiral analysis.
Related Technical Resources
For branched, labeled or cyclic targets requiring Dap incorporation, Alan Scientific can evaluate the sequence through our advanced modified peptide synthesis service.