Boc-His(1-Boc)-OSu is a Boc-protected histidine derivative in which the imidazole side chain is additionally protected as a Boc carbamate and the alpha-amino group is protected by a Boc group, forming a protected amino acid N-hydroxysuccinimyl (OSu) ester. The molecule contains a carboxyl group converted to the OSu active ester for acyl transfer, while the histidine imidazole functionality is masked by the second Boc group to control chemoselectivity and suppress undesired side reactions during coupling. In peptide synthesis and related amide-bond formation workflows, this protected, activated derivative is used as an acylating reagent to introduce the doubly Boc-protected histidine residue under conditions where the OSu ester can react with nucleophiles such as amines to generate protected peptide intermediates.
Boc-His(1-Boc)-OSu is a protected histidine derivative featuring an N-terminal Boc group and an additional Boc-protected imidazole side chain, converted to an N-hydroxysuccinimide (OSu) ester for acyl transfer. This activated ester form is widely used to prepare histidine-containing peptide segments and to introduce the protected histidine residue under conditions that favor coupling efficiency while maintaining side-chain protection. The combination of Boc protection and the OSu leaving group makes it particularly relevant for peptide chemistry workflows and for preparing protected intermediates where histidine's imidazole needs to remain masked during assembly.
1. Solid-Phase Peptide Coupling
Boc-His(1-Boc)-OSu is used as a histidine building block in peptide synthesis workflows where the imidazole side chain must remain protected throughout chain assembly. Peptide synthesis groups and custom peptide manufacturers select this OSu-activated format to promote efficient amide bond formation during stepwise coupling, while the Boc groups help prevent side reactions from the histidine functionality. In practice, it supports the preparation of protected histidine-containing sequences for downstream deprotection and purification, including peptides used in structure-function studies and synthetic standards.
2. Segment Condensation Intermediates
Boc-His(1-Boc)-OSu is commonly applied in segment condensation and solution-phase intermediate assembly when a protected histidine residue is required as a defined acyl component. Researchers developing longer peptide constructs or preparing peptide fragments for later ligation benefit from the OSu ester activation, which provides a controlled electrophilic handle for forming the next peptide bond without exposing the imidazole to undesired chemistry. This makes the reagent a practical choice for pharmaceutical intermediate development teams that need reliable, protected building blocks to build sequence-defined intermediates prior to global deprotection.
3. Protected Histidine Acylation
Boc-His(1-Boc)-OSu serves as an activated acylating agent for introducing a Boc-protected histidine unit into protected amines under synthetic conditions compatible with Boc retention. Chemical biology and medicinal chemistry groups use this type of OSu ester to generate histidine-containing protected derivatives that can be carried forward into peptide conjugation strategies or into the synthesis of peptidomimetic scaffolds. The masked imidazole side chain is a key feature, enabling controlled downstream transformations where histidine's reactivity must be suppressed until a planned deprotection step.
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