Syntheses of isotopically labelled L-α-amino acids with an asymmetric centre at C-3

Approaches are described to the synthesis of a series of isotopically labelled L-alpha-amino acids each with an asymmetric centre at C-3, including isoleucine, allo-isoleucine, threonine and allo-threonine. The methods may be simply adapted for the selective incorporation of an isotopic label at each site of L-valine including the selective labelling of either diastereotopic methyl group with carbon-13 and/or deuterium and labelling of the amine with nitrogen-15.