New Hydrophobic Vitamin B₁₂ Derivatives via Ring-Opening Reactions of <i>c</i>-Lactone

A selective synthesis of new hydrophobic cobalamin derivatives bearing two different spacers has been accomplished via ring-opening reaction of c-lactone. The reaction of c-lactone with various amines afforded three types of amides (a, b, and c) depending on the reaction conditions. The structure of lactone b was determined by the X-ray analysis confirming the position of ring closure. It also reveals the presence of a hydrogen bond between the terminal hydroxy group and one of the axial cyanide ligands.