Synthesis of β‐alanyl‐arginyl‐glycyl‐phenylalanyl‐phenyl‐alanyl‐typosine amide labelled with tritium or carbon‐14

The synthesis of β‐Ala‐Arg‐Gly‐Phe‐Phe‐Tyr‐NH 2 labelled with tritium on the tyrosine residue or with carbon‐14 on the arginine residue is described. The tritium labelled compound VII was prepared in 49% radiochemical yield from L‐[3, 5‐ 3 H] tyrosine and benzyloxycarbonyl‐β‐alanyl‐nitro‐arginyl‐glycyl‐phenylalanyl‐phenylalanine. The carbon‐14 labelled compound XVI was synthesized in 17% radiochemical yield from L‐[U‐ 14 C]arginine and glycyl‐phenylalanyl‐phenylalanyl‐tyrosine amide.