Studies on development of the selective oxygenation catalysts based on mimicking function of nonheme monoiron oxygenases

随后进行了非血红素单铁配合物和锰配合物的类加氧酶催化功能的研究，并阐明了对底物活化至关重要的电子转移机制。1)单铁配合物对儿茶酚醇内、外二醇的氧化裂解研究了三足配体和三齿配体连接的单铁配合物对儿茶酚氧合的催化活性。取代基的电子和空间效应对选择性醇内裂解的影响为氧活化和氧插入C-C键的过程提供了重要信息。铁配合物与三齿配体的外醇解理也阐明了氧与铁中心直接结合的氧化机制。不仅使用仅含有N结合位点的配体，还使用含有N和O结合位点的配体来澄清O2插入儿茶酚。通过模拟含锰的外二醇裂解加氧酶，首次合成了锰(II)-半醌配合物。这些配合物被氧化生成了醇内裂解产物。有趣的是，氧的可逆吸收被观察到，表明分子氧首先结合到金属中心（铁和锰），然后结合到儿茶酚碳。3)铁配合物与水溶性配体在水中的氧化虽然酶促氧化在水介质中进行，但在有机溶剂中进行了模型氧化。这部分是由于配体只溶于有机溶剂，部分是由于排除了除分子氧以外的氧源。我们首先开发了一个模型系统，该系统在水中工作，通过使用具有磺酸取代基的TPA配体，对单烷基儿茶酚（例如4-丁基儿茶酚）、具有氯和羧酸盐等抽电子取代基的儿茶酚进行选择性的醇内裂解。重要的是发现原儿茶酸被单铁络合物氧化裂解，因为尽管最常用的酶原儿茶酸加氧酶尚未开发出模型加氧。研究还发现，介质的pH值控制对水体系至关重要。我们还发现，不含磺酸取代基的TPA配合物在水介质中也能有效地进行反应。少

Following studies were performed on the development of oxygenase-like catalytic functions by nonheme monoiron complexes and manganese complexes and on the clarification of mechanisms of electron transfer that is essential for activation of substrates.1)Intradiol and extradiol oxygenative cleavage of catechols by monoiron complexesCatalytic activity of oxygenations by monoiron complexes ligated by tripodal ligands and tridentate ligands were studied. Effect of electronic and steric effects of substituents on the selective intradiol cleavage gave important information of the oxygen activation and oxygen insertion process into the C-C bonds. In the extraiol cleavage by iron complexes with tridentate ligands also clarified the mechanism of oxygenation via the direct oxygen binding to the iron center. Not only ligands with only the N binding sites but also ligands with N and O binding sites were used for clarification of the O2 insertion into catechols.2)Intra and extradiol oxygenative clea … More vage of catechols by manganese complexesBy mimicking manganese-containing extradiol cleaving oxygenases, Mn(II)-semiquinone complexes were first synthesized. The complexes were found to be oxygenated to give the intradiol cleavage productws. Interestingly, the reversible uptake of oxygen was observed, indicating that the molecular oxygen binds first to the metal center (iron and manganese) prior to binding to the catechol carbon.3)Oxygenations in water by iron complexes with water-soluble ligandsAlthough enzymatic oxygenations proceeds in aqueous media, models oxygenations have been performed in organic solvents. This is partly due to the ligands soluble only in organic solvents, and partly on exclusion of oxygen saurce other than molecular oxygen. We have first developed a model system that works in water to give the selective intradiol cleavage of mono-alkyl catechols, e.g. 4-butyl catechols, catechols with the electron-withdrawing substituents, such as chloro and carboxylate, by using the TPA ligands with sulfonate subsitutients. It is important to find that the protocatechuic acid was found to be oxygenatively cleaved by monoiron complexes, because the model oxygenation has not be developed in spite of the most popular enzyme, protocatechuic oxygenases. It was also found that the pH control of the media is essential for the aqueous system. We also found that the TPA complexes without the solfonate substituents are also effective for the reaction in aqueous media. Less