Synthesis of specifically labeled peptides

The unnatural labeled amino acid N-acetyl-D-3-(2-naphthyl)-[2,3-3H] alanine having a specific activity of 43.7 Ci/mmol was obtained in 98.7% optical yield by asymmetric reduction of 2-N-acetylamino-3-(2-naphthyl)acrylic acid with tritium gas in the presence of the chiral homogeneous catalyst (S,S)BPPM-Rh+. This amino acid was used in a microscale solution phase synthesis of the labeled LHRH antagonist [Ac-D-(2,3-3H) Nal1, D-p-Cl-Phe2, D-Trp3, D-hArg (Et2)6, D-Ala10] LHRH. The chiral synthesis of labeled amino acids as a strategy for the general synthesis of labeled peptides is discussed.