Tritiated peptides. Part 13. Synthesis of [4,5-3H-Leu2]- and [3,4-3H-Pro6]-locust adipokinetic hormone

Abstract
The synthesis of [4,5-3H-Leu2]- and [3,4-3H-Pro6]-locust adipokinetic hormones by the catalytic tritiation of [4,5-dehydroLeu2]-(ΔLeu2-) and [3,4-dehydroPro6]-(ΔPro6-) precursors is described. The products had specific radioactivities of 115 and 12.1 Ci mmol–1 respectively. The distribution of isotope in the former was investigated by 3H n.m.r. spectroscopy which confirmed the conclusions from 2H n.m.r. spectroscopy of catalytically deuteriated N-acetyl-4,5-dehydroleucine. It was concluded that the δ-methyl groups and the γ-methinyl group of leucine are the only tritiated positions in the molecule.