An Inversion of Threonine to Allothreonine in the N,o-Migration Reaction of Threonine Peptides in Concentrated Sulfuric Acid

In a N,O-migration reaction of peptides containing β-hydroxy-α-amino acids in strong acids, it was generally accepted that the configuration on β-carbon atom is retained through the reaction. However, according to our recent investigation using concentrated sulfuric acid as strong acid, a configurational change was observed in the migration reaction. Thus, the threonine residue in peptides was converted to allothreonine residue on the reaction. For the migration reaction accompanying an inversion of configuration, we suggested the mechanism involving SN2 elimination of O-sulfate of threonine residue.