Study of the chemical reactivity of nitric oxide and other related biological redicals

一氧化氮（NO）是生物自由基分子之一，是多种生理功能的重要介质。然而，高浓度的NO的形成引起细胞毒性。NO与包括分子氧在内的各种活性氧物种快速反应以产生高度氧化的氮氧化物，因此NO的固有反应性仍不清楚。我们一直在研究NO在有氧或无氧条件下的反应性，并选择氮杂化合物作为反应底物。氮杂化合物与氮氧化物的反应是已知的，但反应的活性物种却很少报道。通过控制混合物中分子氧的含量，NO对各种氮杂化合物（包括胺、肼和酰胺）都表现出温和的选择性反应，在此基础上，我们将该反应体系应用于其他氮杂化合物，发现具有代表性的羰基衍生物缩氨基脲与NO在氧气存在下反应，得到了高产率的母体羰基化合物。这是缩氨基脲转化为母体羰基化合物的第一个实例。

Nitric oxide (NO) is one of the biological radical molecules, and plays important roles as a mediator of various physiological functions. Formation of NO in high concentration, however, causes cytotoxicity. NO reacts rapidly with various active oxygen species including molecular oxygen to give highly oxygenated nitrogen oxides, thus the intrinsic reactivity of NO remains unclear. We have been investigating the reactivity of NO in the presence or absence of oxygen, and selected aza compounds as substrates for the reaction. Although aza compounds have been known to react with nitrogen oxides, the active species of the reactions were seldom reported. By controlling the amount of molecular oxygen in the mixtrue, NO did show a mild and selective reactivity toward various aza compounds including amines, hydrazines, and amides.With these precedents in hand, we next applied the reaction system to other aza compounds, and found that semicarbazones, which are among the representative carbonyl derivatives, react with NO in the presence of oxygen to give parent carbonyl compounds in good yields. This is the first example that the semicarbazones were converted to parent carbonyl compounds.