Fmoc-OSu is an activated succinimidyl carbonate used to introduce the 9-fluorenylmethoxycarbonyl (Fmoc) protecting group onto amino functions. It is widely used in preparation of Fmoc-protected amino acids, specialty peptide building blocks and other amine-containing intermediates for peptide and organic synthesis.

Also described as Fmoc-NHS, Fmoc succinimidyl carbonate or N-(Fmoc-oxy)succinimide, Fmoc-OSu transfers the base-labile Fmoc group through reaction of an activated carbonate with a nucleophilic amine.

Product Information

How Fmoc-OSu Is Used

Fmoc-OSu reacts with suitable amino groups to form Fmoc carbamates. The succinimidyl carbonate acts as an activated Fmoc donor, allowing preparation of protected building blocks that can later undergo standard base-mediated Fmoc removal.

Novabiochem describes Fmoc-OSu as a reagent for preparation of pure Fmoc-amino acids with reduced contamination by Fmoc-dipeptide by-products in appropriate derivatization protocols.

Applications in Peptide Building-Block Preparation

Fmoc-OSu can be used to prepare Fmoc derivatives of standard and non-natural amino acids, amino-containing linkers, peptide fragments and functionalized amines. It is also useful in synthetic workflows where selective installation of a removable aromatic carbamate is required.

Published applications extend beyond routine amino-acid protection to selective amine functionalization and specialized building-block preparation.

Fmoc-OSu vs Fmoc-Cl

Fmoc-OSu and Fmoc chloride both introduce Fmoc protection, but they are different electrophilic reagents with different leaving groups and reaction profiles. The best choice depends on substrate solubility, competing functional groups, pH/base conditions and purification requirements.

Fmoc-OSu should therefore not be described as universally “better” than Fmoc-Cl; its advantage is that it provides an alternative activated-carbonate route with well-established use in amino-acid derivatization.

Fmoc-OSu vs Z(2-Br)-OSu

Z(2-Br)-OSu installs the 2-Br-Z protecting group used particularly in Boc-oriented tyrosine protection, whereas Fmoc-OSu installs base-labile Fmoc on amines. These two succinimidyl reagents support different protection strategies.

Application Scope

Typical uses include N-Fmoc protection of amino acids, preparation of specialty peptide building blocks, derivatization of amino-functional molecules and research-scale synthesis of protected intermediates.

Fmoc-OSu is a reactive synthetic reagent and not a direct in vitro or in vivo assay compound.

Safety and Procurement Considerations

Current major supplier safety information classifies Fmoc-OSu as harmful if swallowed (H302), capable of causing an allergic skin reaction (H317), and toxic to aquatic life with long-lasting effects (H411). Review the product-specific MSDS before handling and prevent unnecessary environmental release.

For procurement, confirm CAS 82911-69-1, formula, assay, moisture-sensitive handling requirements and lot-specific analytical identity.

Product Documents

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

MSDS_Fmoc-OSu_AS2002

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 Fmoc-OSu used for?

It is used to introduce Fmoc protection onto amino acids, amines and other amino-containing synthetic intermediates.

Is Fmoc-OSu the same as Fmoc-Cl?

No. Both transfer Fmoc, but they are different reagents with different leaving groups and reaction conditions.

Can Fmoc-OSu be used to make non-natural Fmoc amino acids?

Yes. It is commonly used in preparation of Fmoc-protected amino-acid derivatives when the substrate and protection strategy are compatible.

Related Technical Resources

Explore additional Specialty Peptide Building Blocks for protected fragments, linker motifs and peptide-synthesis intermediates.

For sequence-specific synthesis, protected-fragment assembly and modified peptide projects, see our Chemical Peptide Synthesis service.

Research Use Only.