Synthesis of 15N omega-hydroxy-L-arginine and ESR and 15N-NMR studies for the elucidation of the molecular mechanism of enzymic nitric oxide formation from L-arginine.

N omega-Hydroxy-L-arginine (2) was prepared by a multi-stage synthesis; the key step was the addition of hydroxylamine to the protected cyanamide 8. The presence of N-hydroxyguanidines was confirmed, above all, by 15N-NMR investigations. 15N omega-Hydroxy-L-arginine (2) was converted quantitatively to 15NO by NO synthases from macrophages. 15NO was identified by ESR-spectroscopy. These experiments confirm that 15N omega-hydroxy-L-arginine (2) is an intermediate in the biosynthesis of NO from arginine (1) and that the N-hydroxylated N-atom is present in the NO formed.