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

研究了非血红素单铁络合物和锰络合物类加氧酶催化功能的发展，阐明了底物活化所必需的电子传递机理。1)单铁络合物对儿茶酚的内醇和外氧化裂解。取代基的电子和空间效应对分子内选择性裂解的影响提供了氧活化和氧插入C-C键过程的重要信息。在铁与三齿配体形成的络合物裂解外醇的过程中，还阐明了氧直接与铁中心结合的氧化机理。不仅只有N结合位的配体，而且有N和O结合位的配体也被用来阐明O2插入到儿茶酚中。2)醇内和醇外氧合CleA…模拟含锰外切加氧酶，首次合成了锰(II)-半喹酮配合物。研究发现，这些络合物是被氧化的，从而得到了Instriol的裂解产物。有趣的是，观察到氧的可逆吸收，表明分子氧在与邻苯二酚碳结合之前首先结合到金属中心(铁和锰)。3)水中铁与水溶性配体的络合物的氧化虽然酶促氧化是在水介质中进行的，但在有机溶剂中也进行了模型氧化。这部分是由于配体只能溶于有机溶剂，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体系，通过使用带有磺酸盐取代基的TPA配体，在水中选择性地裂解单烷基儿茶酚，如4-丁基儿茶酚，带有吸电子取代基的儿茶酚，如氯代和羧酸盐。重要的是发现原儿茶酸被单铁络合物氧化裂解，因为尽管最流行的酶原儿茶酸加氧酶还没有形成模型氧合。研究还发现，介质的pH控制对于水体系是必不可少的。我们还发现，不含磺酸盐取代基的TPA络合物在水介质中对反应也是有效的。较少

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