meso-Modified Cobalamins: Synthesis, Structure, and Properties.

Vitamin B12 and its derivatives present excellent paradigms for bioinspired catalysis. The inherent challenges for derivatizing cobalamins, such as vitamin B12 , to incorporate them in supramolecular designs and materials, limit the range of their utility and applications. Herein, we present a synthetic approach toward derivatives of vitamin B12 possessing electron-donating and -withdrawing substituents at the meso position (C10). Spectroscopic and cyclic voltammetry studies reveal that changes in the substitution pattern on the equatorial ligand have a significant impact on the electronic and optical properties of the cobalamin. These synthetic methods, therefore, provide invaluable routes not only for covalent linking to other structures, but also for attaining a wide range of functionalities for the derivatives of vitamin B12 .