1. Ring Around the Cobalt: Vitamin B12
“VitaminB12,the beautiful: excitement will not cease!”
-Albert Eschenmoser
Ring Around the Cobalt: Vitamin B12
Cassie Gates
Advanced Bioinorganic
Dr. Sharon Burgmayer

2. Getting to Know Your Cobalamins
R- Group
Name CN
Cyanocobalamin
CH3
Methylcobalamin
5’-deoxyadenosyl
Adenosylcobalamin OH
Hydroxycobalamin D C

3. Making a State-ment Co–C bond for Cyanocobalamin (1.86 Å) is short
MeCbl and AdoCbl the Co–C bond is longer ( 1.98 Å and 2.0 Å)
Homolytically - Co(II) and an alkyl free radical R
Heterolytically – either Co(I) and R+ or Co(III) and R–

4. Enzyme Time +1 +3 +2

5. B12, what is it good for? Absolutely, nothing everything

6. Go with your Gut

7. The Anti-Villian of Vitamins

8. Gray: C atoms of the corrin unit Yellow: C atoms of the phenyl ligands
Dark red: Co atom
Blue: N atoms
Light red: O atoms
Two projections of a model of the structure of EtPhCbl derived from X‐ray crystal‐structure analysis. Gray: C atoms of the corrin unit, yellow: C atoms of the phenyl ligands, dark red: Co atom, blue: N atoms, light red: O atoms.
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Angewandte Chemie International Edition Volume 52, Issue 9, pages , 13 FEB 2013 DOI: /anie

9. Equilibrium Dissociation Constant of EtPhCbl
IF (k+=7.9×107 M−1 s−1)
TC (k+=9.3×107 M−1 s−1) TC (k−<4×10−6 s−1)
IF (k−<5×10−6 s−1)
Equilibrium Dissociation Constant of EtPhCbl
Kd≈2×10−14 M

10. Got it on Lock!
So where from here?

11. Questions to Consider Why cobalt? Why DMB?
What else could be used as a good R-group for an anti-vitamin B12? (characteristics should it have?)
Why is this useful?
+ CN - 

12. Bibliography
Kroner, Zina (2011). Vitamins and Minerals. Vitamin B12. Retrieved from Perry, C., Marques, H. (2004), Fifty years of X-ray crystallography of vitamin B12 and its derivatives. South African Journal of Science. July/August. 100 Ruetz, M., Gherasim, C., Gruber, K., Fedosov, S., Banerjee, R. and Kräutler, B. (2013), Access to Organometallic Arylcobaltcorrins through Radical Synthesis: 4- Ethylphenylcobalamin, a Potential “Antivitamin B12” . Angew. Chem. Int. Ed., 52: 2606–2610. doi: /anie