Catalytic Activity of Novel Vitamin B12 Derivatives
We have developed the synthesis of novel cobalamin derivatives possessing modified substituents at the periphery of the molecule. Our methodology presents a unique situation in which the six peripheral amide groups are transformed while leaving the bottom “f-loop” intact.2 These derivatives displayed UV-Vis spectra and oxidation-reduction characteristics similar to those of vitamin B12 but they differed significantly from the”incomplete” corrinoid heptamethyl cobyrinate, where the nucleotide moiety is absent, and instead, the second cyanide is coordinated. We confirmed that the intramolecular coordinating ligand plays a role in the radical reactions catalyzed by vitamin B12 derivatives. For example, the microwave-assisted homocoupling of benzylbromide3 catalyzed by cobalester produced a higher yield when compared to reactions catalyzed by reduced (CN)2Cob(OMe)7.Furthermore, the amphiphilic character of these newly synthesized derivatives facilitates carbon insertion into the vinyl C-H bond of olefins with alkyl diazoacetates in the presence of light.
1. Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999
2. Proinsias ó, K.; Giedyk, M.; Sharina, I.G.; Martin, E. and Gryko, D. ACS Med. Chem. Lett. 2012, 3, 476.
3. Giedyk, M.; Fedosov, S.; Gryko, D. Chem. Commun. 2014, 50, 4674-4676.