Fmoc-Sar-OPfp: identity and synthesis considerations
Fmoc-Sar-OPfp is the pentafluorophenyl ester of Fmoc-protected sarcosine, or N-methylglycine. It combines an activated carboxyl group with an Fmoc-protected nitrogen for introducing a sarcosine residue into a peptide or related amide. Sarcosine has no alpha-carbon stereocenter; its methyl group is attached to nitrogen, not to the alpha carbon.
| Catalog No. | AS4170 |
|---|---|
| CAS No. | 159631-29-5 |
| Molecular formula | C24H16F5NO4 |
| Molecular weight | 477.38 g/mol |
What the active ester changes
The OPfp group provides an activated acyl donor for reaction with a free amine. It is not the free acid Fmoc-Sar-OH and should not automatically be assigned the same activation recipe. Select solvent, base and reaction time around the receiving amine and substrate compatibility, and monitor conversion rather than assuming that preactivation guarantees complete coupling.
Sarcosine incorporation versus the next coupling
Two operations need separate planning. During incorporation, the receiving amine reacts with the sarcosine active ester. After Fmoc removal, the newly exposed sarcosine nitrogen is a secondary amine, so the following acylation can behave differently from coupling onto a primary amino group. A method that works for insertion may therefore need adjustment for chain extension. Remove residual Fmoc-deprotection amine before introducing an active ester.
Choosing an active ester for the target residue
For an activated serine building block, Fmoc-Ser(tBu)-OPfp retains a protected side-chain hydroxyl and a chiral amino-acid center. This comparison separates the shared OPfp activation strategy from residue-specific chemistry. For a sequence containing several N-substituted residues, chemical peptide synthesis support can help frame a discussion of coupling checkpoints and analytical requirements.
Handling and analytical planning
Limit unnecessary moisture exposure because hydrolysis consumes the active ester. Follow the supplied lot label for storage and allow a sealed refrigerated container to equilibrate before opening to reduce condensation. Product identity, residual starting material and sequence completion require suitable analytical checks; a single successful coupling is not evidence of improved peptide potency or stability.
Product Documents
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
Is Sar the same as alanine?
No. Sarcosine is N-methylglycine. Alanine has a methyl substituent on the alpha carbon and a different nitrogen substitution pattern.
Does this product need carboxyl activation?
It is already a pentafluorophenyl active ester. Additional activation should be justified by the intended method, rather than copied from a free-acid protocol.
Is Fmoc-Sar-OPfp chiral?
Sarcosine has no alpha-carbon stereocenter. The stereochemical properties of a resulting peptide depend on its other residues.
Research Use Only. Not for human or veterinary use.