Palladium‐Catalyzed Oxidation of Glucose in Glycopeptides

Selective modification of carbohydrate residues in glycopeptides is highly relevant as a tool in glycobiology. In particular, oxidation allows for subsequent ligation with a label or handle and can be effectuated enzymatically or chemically. Chemical oxidation of carbohydrate residues in glycopeptid...

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Bibliographic Details
Published in:European journal of organic chemistry 2022-07, Vol.2022 (25), p.n/a
Main Authors: Reintjens, Niels R. M., Yakovlieva, Liubov, Marinus, Nittert, Hekelaar, Johan, Nuti, Francesca, Papini, Anna Maria, Witte, Martin D., Minnaard, Adriaan J., Walvoort, Marthe T. C.
Format: Article
Language:English
Subjects:
Aldehydes
Amino acids
Antibiotics
Biotin
Carbohydrates
Carbonyls
Glucose
Glycopeptides
Mass spectrometry
Oligosaccharides
Optimization
Oxidation
Oxime ligation
Palladium
Palladium catalysis
Residues
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Summary:Selective modification of carbohydrate residues in glycopeptides is highly relevant as a tool in glycobiology. In particular, oxidation allows for subsequent ligation with a label or handle and can be effectuated enzymatically or chemically. Chemical oxidation of carbohydrate residues in glycopeptides is nearly invariably done using periodate cleavage, leading to aldehydes. In this work, we applied palladium‐catalyzed oxidation for the same purpose. The catalyst, [(neocuproine)PdOAc]2OTf2, developed for the site‐selective oxidation of mono‐ and oligosaccharides on preparative scale, proved suitable for the oxidation of glucose residues in a series of glucopeptides. Careful optimization of the reaction conditions is necessary to get acceptable conversions without excessive over‐oxidation of amino acid side‐chains, in particular threonine. The resulting carbonyl function can be used for an oxime‐ligation to biotin. A protocol for the analysis of the products using mass spectrometry is also reported. The development of selective labeling methods to investigate protein glycosylation is a current challenge in glycobiology. This work reports the Pd‐catalyzed oxidation of glucosides in pure glucopeptides and tryptic digest mixtures by using a previously reported method to selectively oxidize the C3‐position of unprotected carbohydrates with [(neocuproine)PdOAc]2OTf2 as catalyst. The obtained keto‐group was further functionalized with a biotin handle through oxime‐ligation.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.202200677