L-[4-l3C]Glutamic acid (1) and L-[4-13C]glutamine (2) were synthesized from sodium [2-13C]acetate (5) and Dellaria's oxazinone 3 as a chiral glycine equivalent. Sodium [2-13C]acetate (5) was converted to [2-13C]acrylate 4. Diastereoselective Michael addition of the enolate of 3 to the acrylate 4 proceeded with high diastereoselectivity to give the adduct 12. Reductive cleavage of the C–S bond, ethanolysis