Boc-D-Cys(Mbzl)-OSu is a protected, stereochemically specified cysteine derivative in which the amino group is protected as a Boc carbamate and the thiol side chain is masked as an Mbzl (benzyl-type thioether) substituent. The molecule also contains an activated N-hydroxysuccinimide (OSu) ester at the carboxyl terminus, providing an electrophilic carbonyl for acyl transfer, while the D-configuration is retained at the α-carbon as indicated by the product name. In peptide and bioconjugation workflows, this OSu ester functions as an acylating intermediate that can react with nucleophiles such as amines to form amide bonds under conditions compatible with Boc and thioether-protected cysteine residues.
CAT No: CP27578
CAS No:90545-10-1
Synonyms/Alias:BOC-D-CYS-OSU;ZINC71788041;90545-10-1
Boc-D-Cys(Mbzl)-OSu is a D-configured cysteine derivative bearing a Boc-protected amino group and an S-Mbzl (benzyl-type) thioether protecting group, supplied as an N-hydroxysuccinimide (OSu) ester. This combination makes the compound a reactive amino acid building block designed for efficient amide bond formation under peptide and bioconjugation-relevant coupling conditions, while the Boc and thioether protection pattern helps maintain side-chain integrity during downstream assembly. The OSu ester functionality is particularly useful when rapid activation and coupling of the carboxylate equivalent are required.
1. Peptide Coupling Building Block
Boc-D-Cys(Mbzl)-OSu is used by peptide chemistry groups to introduce a D-cysteine residue into protected peptide segments where controlled amide bond formation is needed. The OSu ester activation supports efficient coupling to amine-containing partners, enabling assembly of dipeptides and longer sequences in workflows that prioritize reliable coupling efficiency and minimized side reactions. Researchers commonly select this specific protection pattern to keep the cysteine side chain protected as an S-Mbzl thioether during segment condensation, preserving the residue for later deprotection and functionalization steps when required for native cysteine chemistry in the final peptide.
2. D-Cysteine Segment Synthesis
Boc-D-Cys(Mbzl)-OSu supports the preparation of D-cysteine-containing peptide intermediates used in stereochemical studies, peptide library construction, and conformational or proteolysis-resistance investigations where D-amino acid incorporation is a key design variable. In custom peptide manufacturing research, the OSu-activated format helps streamline the coupling step for assembling D-cysteine-bearing fragments that retain side-chain protection throughout purification and handling. The Boc group further provides a standard protection handle for controlled N-deprotection strategies in subsequent synthesis stages, making the reagent practical for iterative segment assembly and purification workflows.
3. Protected Cysteine Bioconjugation Intermediate
Boc-D-Cys(Mbzl)-OSu is also applied as a protected cysteine amino acid intermediate for chemical biology and biomaterials development when a cysteine-derived linkage must be installed while avoiding premature cysteine-side-chain reactivity. The OSu ester enables coupling to primary amines on peptides, linkers, or scaffold molecules, supporting the generation of amide-linked conjugates under conditions compatible with maintaining the protected thioether side chain. Downstream, the protected cysteine motif can be carried into further derivatization steps after the synthesis/conjugation stage, allowing researchers to build defined cysteine-containing conjugates without uncontrolled side reactions during early assembly.
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