Catalytic Synthesis of β3‐Amino Acid Derivatives from α‐Amino Acids

α goes to β! The catalytic ring-expansive carbonylation of oxazolines, easily derived from α-amino acids, to yield β-amino acid derivatives is described. The catalyst is [HCo(CO)4]; high yields are observed for most substrates, and enantiopure oxazolines are carbonylated with predictable stereochemistry to the corresponding enantiopure oxazinones.