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Guanidinium Promoted Cleavage of Phosphoric Diesters: Kinetic Investigations and Calculations Provide Indications on the Operating Mechanism
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acs.joc.7b01925 Riccardo Salvio 1 , Alessandro Casnati 2
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acs.joc.7b01925 Riccardo Salvio 1 , Alessandro Casnati 2
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The catalytic activity of the guanidinium units toward the cleavage of phosphoric diesters is deeply investigated both with kinetic experiments and DFT calculations. The first part of the investigation aims to determine how the structure of the substrate (phenyl or alkyl esters) is able to influence the guanidinium-catalyzed hydrolysis changing the mechanism from ANDN to AN+DN. In the cleavage of the DNA model bis(4-nitrophenyl)phospate (BNPP), experimental kinetic data highlight the operation of a guanidine–guanidinium catalytic dyad that can act both intermolecularly and intramolecularly on different molecular scaffolds exhibiting notable values of effective molarity. 31P NMR spectra and DFT investigation provide indication that the deprotonated guanidine involved in such a catalysis acts as a general base in the deprotonation of a water molecule involved in the cleavage, and not as nucleophilic unit. Moreover, DFT calculations were carried out to determine the guanidinium promoted activation energy of pseudorotation. The results indicate a remarkable drop in the activation energy of this process for dialkylphosphate esters explaining, in part, the higher sensitivity of diribonucleoside to the presence of guanidinium-based catalysts compared to the more activated RNA model HPNP.
中文翻译：
胍盐促进磷酸二酯的裂解：动力学研究和计算为运行机理提供了指示
通过动力学实验和DFT计算，深入研究了胍单元对磷酸二酯裂解的催化活性。调查目标的第一部分以确定所述衬底（苯基或烷基酯）的结构如何能够影响胍催化水解改变从A机构Ñ d Ñ至A Ñ + d Ñ。在DNA模型双（4-硝基苯基）磷酸酯（BNPP）的裂解中，实验动力学数据突显了胍-胍催化二联体的操作，该分子可以在分子间和分子内作用于表现出明显摩尔浓度的不同分子支架。31P NMR光谱和DFT研究表明，参与这种催化作用的去质子化的胍作为裂解中涉及的水分子去质子化的一般碱，而不是亲核单元。而且，进行了DFT计算以确定胍促进的伪旋转的活化能。结果表明该方法对磷酸二烷基酯的活化能显着下降，部分解释了与活化程度更高的RNA模型HPNP相比，双核糖核苷对基于胍基催化剂存在的敏感性更高。
更新日期：2017-09-19
中文翻译：
胍盐促进磷酸二酯的裂解：动力学研究和计算为运行机理提供了指示
通过动力学实验和DFT计算，深入研究了胍单元对磷酸二酯裂解的催化活性。调查目标的第一部分以确定所述衬底（苯基或烷基酯）的结构如何能够影响胍催化水解改变从A机构Ñ d Ñ至A Ñ + d Ñ。在DNA模型双（4-硝基苯基）磷酸酯（BNPP）的裂解中，实验动力学数据突显了胍-胍催化二联体的操作，该分子可以在分子间和分子内作用于表现出明显摩尔浓度的不同分子支架。31P NMR光谱和DFT研究表明，参与这种催化作用的去质子化的胍作为裂解中涉及的水分子去质子化的一般碱，而不是亲核单元。而且，进行了DFT计算以确定胍促进的伪旋转的活化能。结果表明该方法对磷酸二烷基酯的活化能显着下降，部分解释了与活化程度更高的RNA模型HPNP相比，双核糖核苷对基于胍基催化剂存在的敏感性更高。
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