Amino Acid Transformation Mediated upon Metal Complex as a Apoenzyme-Coenzyme-Substrate Model

在三元金属配合物上模拟了吡哆醛辅酶催化的氨基酸转化。利用Co（II）或Co（III）配合物与2,2':6',2"-三联吡啶（terpy）和水杨酸-氨基酸（SAS）进行了新型氨基酸的氧化转化。这里，三元配合物[Co(sas)(terpy)]中的terpy被认为是一种脱酶模型，水杨醛被认为是一种辅酶模型，氨基酸被认为是一种底物模型。在有氧条件下的弱碱性培养基中，氨基酸的α位置被氧化生成水杨酸- α -羟基氨基酸（SEAS）复合物[Co(shas)(terpy)]。在质谱和ESR研究的基础上确定了SHAS α位置取代羟基的氧原子来源于分子氧。sas和terpy配体之间的配体间相互作用在反应控制中起着重要作用。这种α -羟基化作用被CH-pi相互作用抑制，这是由氨基酸侧链和terpy平面上的&和-甲基邻近引起的。本文还讨论了其他三元配合物介导的CH-pi相互作用。

Amino acid transformations catalyzed by pyridoxal coenzyme were mimicked non- enzymatically on ternary metal complexes. New type oxidative transformation of amino acids were carried out using by the Co(II) or Co(III) complexes with 2,2' : 6', 2"-terpyridine (terpy) and salicylidene-amino acid (SAS). Here, terpy in the ternary complex, [Co(sas)(terpy)], is considered as a apoenzyme model, salicylaldehyde is as a coenzyme one, and amino acid is as a substrate one. In weakly alkaline media under aerobic condition, the alpha-position of amino acid was oxidized to give a salicylidene-alpha-hydroxyamino acid (SEAS) complex, [Co(shas)(terpy)]. Oxygen atom of the hydroxyl group substituted at alpha-position of SHAS was derived from molecular oxygen, which was determined on the basis of mass spectra and ESR study. Interligand interactions between sas and terpy ligands play an important role for the reaction control. This alpha-hydroxylation is inhibited by the CH-pi interaction, which is caused by the proximity of & and gamma-methyl groups of amino acid sidechain and terpy plane. CH-pi interaction mediated upon the other ternary complexes is also discussed in this report.