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首页> 外文期刊>Chinese science bulletin >Structure, reactivity and mechanism: A comparison of reactivities of the two NAD(P)H models, BNAH and Hantzsch ester
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Structure, reactivity and mechanism: A comparison of reactivities of the two NAD(P)H models, BNAH and Hantzsch ester

机译：结构，反应性和机理：BNAH和Hantzsch酯这两种NAD（P）H模型的反应性比较

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The reduced form of the nicotinamide-adenine dinucleotide coenzyme (NAD(P)H) plays an important role in many bio-reductions by transferring a hydride ion or an electron to the surrounding substrate (see eq. (1), R represents adenine dinucleotide). Thechemical modification of its active site, ie. the 1,4-dihydropyridine ring, is of particular importance, because it can help people to develop new effective catalysts under mild reaction conditions and to understand the mechanisms of the NAD(P)H mediated reductions, i.e. the one-step H~- transfer and multi-step H~- transfer initiated first by electron transfer (e~-H~+-e~- or e~-H-). Studies on the relationships between structure and reactivity have shown that (i) the substituent on the ring nitrogen has a direct influence on the model's reactivity, implying that the driving force for the reduction originates from the removal of single electron (in the case of electron transfer mechanism) or two electrons (in the case of one-step H~- transfer mechanism) from the ring nitrogen, and (ii) the stereochemical course during this redox reaction is affected by the orientation of the 3-carbonyl dipole which has to be syn to the transferring hydride so that the reaction will occur. Although great efforts have been made to better understand the mechanistic details of the NAD(P)H mediated reactions in the past, little has been known, however, about the relationship amongst structure, reactivity and various mechanisms. Here we report our recent kinetic investigation using two different substrates, 5-nitroisoquinolinium ions (1) and ferricyanide ions (2), which may serve as mechanistic probes for hydride transfer and single electron transfer (ET), respectively. The two structurally significantly different models, 1-benzyl-1,4-dihydronicotinamide (BNAH, 3) and Hantzsch ester (H.E., 4), were used in order to understand the structure-reactivity-mechanism relationship and to test the utility of this new method in differentiating the two controversial mechanisms.
机译：烟酰胺-腺嘌呤二核苷酸辅酶（NAD（P）H）的还原形式通过将氢离子或电子转移到周围的底物上而在许多生物还原中起重要作用（参见式（1），R代表腺嘌呤二核苷酸） ）。其活性部位的化学修饰，即1,4-二氢吡啶环特别重要，因为它可以帮助人们在温和的反应条件下开发新的有效催化剂，并了解NAD（P）H介导的还原反应的机理，即一步一步H〜-转移和多步H〜-转移首先通过电子转移（e〜-H〜+ -e〜-或e〜-H-）启动。对结构与反应性之间关系的研究表明：（i）环氮上的取代基对模型的反应性具有直接影响，这意味着还原的驱动力源于单个电子的去除（在电子的情况下）转移机理）或来自环氮的两个电子（在单步H〜-转移机理的情况下），以及（ii）此氧化还原反应过程中的立体化学过程受3-羰基偶极子取向的影响，与转移的氢化物同位，以便发生反应。尽管过去已经做出了很大的努力来更好地理解NAD（P）H介导的反应的机理细节，但是关于结构，反应性和各种机理之间的关系知之甚少。在这里，我们报告我们最近的动力学研究，使用两种不同的底物5-硝基异喹啉鎓离子（1）和铁氰化物离子（2），它们分别可用作氢化物转移和单电子转移（ET）的机理探针。为了了解结构-反应-机理之间的关系并测试其实用性，使用了两种结构上明显不同的模型，即1-苄基-1,4-二氢烟酰胺（BNAH，3）和汉茨酯（HE，4）。区分两种有争议机制的新方法。

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