Fmoc-OBT, more commonly written Fmoc-OBt, is 9-fluorenylmethyl 1-benzotriazolyl carbonate, an activated carbonate used to introduce the Fmoc protecting group onto amino functions. It provides an alternative Fmoc-transfer route to Fmoc-Cl and Fmoc-OSu in the preparation of protected amino acids, glycopeptide components and specialty peptide building blocks.

The benzotriazolyl carbonate acts as an activated Fmoc donor. Because Fmoc is base-labile after installation, Fmoc-OBt is useful when the downstream synthetic strategy requires standard Fmoc deprotection while preserving acid-labile side-chain protecting groups.

Product Information

Fmoc-OBt as an Fmoc Transfer Reagent

Fmoc-OBt reacts with suitable amines to form Fmoc carbamates. It is used in peptide chemistry when a chemist needs to prepare an N-Fmoc-protected amino acid, non-natural amino acid or other amine-containing synthetic intermediate.

Published supplier literature also identifies applications in preparation of protected phosphotyrosine analogs and complex glycopeptide components, illustrating that the reagent is useful beyond routine derivatization of standard amino acids.

Fmoc-OBt vs Fmoc-OSu

Fmoc-OSu and Fmoc-OBt are both activated carbonate Fmoc donors, but they contain different leaving groups. Fmoc-OSu uses an N-hydroxysuccinimide-derived leaving group, whereas Fmoc-OBt uses a benzotriazole-derived leaving group.

The preferred reagent depends on substrate nucleophilicity, solvent, base, side-functionalities, workup and impurity profile. They should not be treated as identical reagents merely because both install Fmoc.

Fmoc-OBt vs Fmoc-Cl

Fmoc-Cl is a reactive chloroformate and is widely used for Fmoc derivatization. Fmoc-OBt offers an activated benzotriazolyl carbonate route without using the chloroformate leaving group.

For process selection, compare reaction rate, hydrolytic sensitivity, substrate compatibility, safety profile and downstream purification rather than assuming one Fmoc reagent is universally superior.

Application Scope

Applications include N-Fmoc protection of standard and non-natural amino acids, preparation of peptide-synthesis building blocks, protected glycopeptide components, amine derivatization and specialty organic synthesis.

Fmoc-OBt is a synthetic protection reagent and is not intended as a direct biological assay compound.

Safety and Procurement Considerations

Current supplier safety information classifies Fmoc-OBt as an irritant associated with H315, H319 and H335. Use suitable ventilation, gloves and eye protection, and minimize dust generation.

For procurement, confirm CAS 82911-71-5, the OBt rather than OSu leaving group, formula, assay and lot-specific identity. Fmoc-OBt and Fmoc-OSu have similar purposes but different molecular identities and molecular weights.

Product Documents

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

MSDS_Fmoc-OBT_AS3014

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-OBT used for?

It is used to introduce Fmoc protection onto amino groups in amino acids and other synthetic intermediates.

Is Fmoc-OBT the same as Fmoc-OSu?

No. Both transfer Fmoc, but Fmoc-OBt contains a benzotriazolyl leaving group and Fmoc-OSu contains a succinimidyl leaving group.

Is Fmoc-OBT the same as Fmoc-Cl?

No. Fmoc-Cl is a chloroformate, while Fmoc-OBt is an activated benzotriazolyl carbonate.

Related Technical Resources

Explore additional Specialty Peptide Building Blocks and Fmoc-transfer reagents.

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