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Updated: Jul 14, 2026

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
Published on: November 22, 2014
Model studies for the thiol-mediated methyl transfer to corrinoids
Christina Wedemeyer-Exl1, Tamis Darbre, Reinhart Keese
1Department of Chemistry and Biochemistry, University of Bern, Freiestr. 3, 3012, Bern, Switzerland.
This study investigated thiol-dependent methylation of cob(II)yrinate using methyl iodide and tosylate. Thiol-mediated methylation occurred with methyl iodide, but methyl tosylate reactivity varied with thiol acidity.
Area of Science:
- Organometallic Chemistry
- Cobalamin Chemistry
- Methylation Reactions
Background:
- Heptamethyl cob(II)yrinate is a key intermediate in cobalamin chemistry.
- Thiol-dependent reactions are crucial in biological and chemical methylation processes.
- Understanding methylation mechanisms is vital for synthetic and catalytic applications.
Purpose of the Study:
- To explore the thiol-dependent methylation of heptamethyl cob(II)yrinate.
- To compare the reactivity of methyl iodide and methyl tosylate as methylating agents.
- To elucidate the mechanistic pathways involved in these methylation reactions.
Main Methods:
- Reaction of heptamethyl cob(II)yrinate with various thiols.
- Monitoring of complex formation using UV-Vis spectroscopy.
- Methylation reactions with methyl iodide and methyl tosylate under different conditions.
- Investigation of inhibitor effects (pyridine, N-methylimidazole) and thiol acidity.
Main Results:
- Co(I) complex formation was observed only with hexane thiol.
- Thiol-mediated methylation with methyl iodide occurred under most conditions.
- Methyl tosylate methylation showed different reactivity, inhibited by pyridine/N-methylimidazole, and dependent on thiol acidity.
Conclusions:
- Thiol-mediated methylation of cob(II)yrinate is feasible with methyl iodide.
- Methyl tosylate presents a distinct reactivity profile, influenced by thiol acidity and specific inhibitors.
- The study provides insights into the mechanistic nuances of cobalamin methylation involving thiols.
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