Figure 1. General structure of corrins/cobalamins.
The figure demonstrates various upper axial ligands, the corrin ring, and a lower axial ligand. Hydroxocobalamin has a hydroxyl group at the R position. Cyanocobalamin has a cyano group at the R position. Methylcobalamin and adenosylcobalamin have a methyl and adenosyl group, respectively, at the R position. Cobinamide lacks the lower axial ligand and has a hydroxyl group at the R position. Dicyanocobinamide has a cyano group as the lower axial ligand and at the R position.
