Isovitamin B 12 : A Vitamin B 12 Derivative That Flips Its Tail

Base on : Vitamin B 12 is well known as a compact and cobalt‐coordinated base‐on corrinoid, in which the corrin and nucleotide moieties are connected by their natural linker, ( R )‐isopropanolamine. In the synthetic isomer, isovitamin B 12 , an n ‐propanolamine linker produces a structural mismatch. X‐ray crystallography revealed two distinct base‐on conformers of isovitamin B 12 (magenta; inward conformer, yellow: outward conformer).