Zinc Substitution of Cobalt in Vitamin B12 : Zincobyric acid and Zincobalamin as Luminescent Structural B12 -Mimics.

Christoph Kieninger,Klaus R Liedl,Joseph A Baker,Klaus Wurst,Evelyne Deery,Steffen Jockusch,Andrew D Lawrence,Maren Podewitz,Martin J Warren,Karl Gruber,Bernhard Kräutler

doi:10.1002/anie.201908428

Abstract

Replacing the central cobalt ion of vitamin B12 by other metals has been a long‐held aspiration within the B12‐field. Herein, we describe the synthesis from hydrogenobyric acid of zincobyric acid (Znby) and zincobalamin (Znbl), the Zn‐analogues of the natural cobalt‐corrins cobyric acid and vitamin B12, respectively. The solution structures of Znby and Znbl were studied by NMR‐spectroscopy. Single crystals of Znby were produced, providing the first X‐ray crystallographic structure of a zinc corrin. The structures of Znby and of computationally generated Znbl were found to resemble the corresponding CoII‐corrins, making such Zn‐corrins potentially useful for investigations of B12‐dependent processes. The singlet excited state of Znby had a short life‐time, limited by rapid intersystem crossing to the triplet state. Znby allowed the unprecedented observation of a corrin triplet (E T=190 kJ mol−1) and was found to be an excellent photo‐sensitizer for 1O2 (ΦΔ=0.70).

Highlights

zincobyric acid (Znby) were produced, providing the first X-ray crystallographic structure of a zinc corrin
The biological use of cobalt as the specific transition metal center in natural B12-cofactors and the interaction between cobalt and the corrin ligand raise intriguing questions concerning the origins of its natural selection.[1]
Engineered B12-biosynthesis[2] has opened up a preparative route to hydrogenobyric acid (Hby),[3] the metal-free corrin ligand of vitamin B12, providing an excellent opportunity for the synthesis of transition-metal analogues of the natural cobaltcorrinoids.[4]

Summary

Citation for published version

Christoph and Baker, Joseph A. and Podewitz, Maren and Wurst, Klaus and Jockusch, Steffen and Lawrence, Andrew D. and Deery, Evelyne and Gruber, Karl and Liedl, Klaus R. and Warren, Martin J. and Kräutler, Bernhard (2019) Zinc Substitution of Cobalt in Vitamin B12 : Zincobyric acid and Zincobalamin as Luminescent Structural B12 -Mimics.

Document Version

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Experimental Section

Conflict of interest