2，3－二甲基－1－对氯苯磺酰基咪唑啉盐与邻氨基苯酚反应的量子化学研究

用量子化学方法对叶酸辅酶模型化合物2，3－二甲基－1－对氯苯磺酰基咪唑 啉盐与邻氨基苯酚的反应进行了理论研究。结果表明，咪唑啉环有两种开环方式， 反应可以通过两种途径实现，得到较稳定的中间体或者实现一碳单元的完全转移。 通过优化计算所有步骤的中间体和过渡态的结构可知，各个中间体和过渡态具有不 同的构型、构象，有些过程的构象变化是进行下一步反应所必需的，在所有过程中 质子转移步骤过渡态的能量最高，是反应的限速步骤。     

The theoretical study of one-carbon unit transfer with H_2O participation from imidazolidine to dUMP analogue

The ONIOM quantum mechanics method is used to study the reaction of one-carbon unit transfer from an imidazolidine to 6- aminouracil model with the participation of water molecules.The computation results show that in this reaction the participation of H_2O molecule makes the energy barrier lower because of the H-bond interaction.     

四氢叶酸辅酶模型的合成及甲基取代的一碳单元转移反应

本文报道了甲基取代的甲酸态的四氢叶酸辅酶模型--碘化1, 2-二甲基-3-对氯苯磺酰基咪唑啉的合成。研究了模型与单官能团亲核体(苯胺、对氯苯胺、对硝基苯胺)和双官能团亲核体(邻苯二胺、邻氨基酚、乙二胺)作用, 转移甲基取代的一碳单元的反应。     

DFT Study on One-carbon Unit Transfer from 1,10-CH^ - tetrahydroquinoxaline to Methylamine

Density Functional Theory (DFT) method was used in this paper to study one-carbon transfer from 1,10-tetrahydroquinoxaline,an analogue of tetrahydrofolic acid.to methylamine.This reaction can be completed via two paths.From the computation results we can conclude that a general-acid catalysis exists in this reaction.By computation we find DFT has its limitation in describing a newly incorporated structure with a unit charge.     

ONIOM study of one‐carbon unit transfer from imidazolidine to dUMP analogue

The ONIOM quantum mechanics method is used in this article to study one‐carbon unit transfer from an imidazolidine to 6‐aminouracil derivates. The computation results show that this reaction can be completed via three paths, owing to the three different proton transfer modes. Each path experiences three processes of nucleophile attacking, proton transferring, and bond rupturing. The focus of discussion falls on the proton transfer process. By analyzing the calculation results, we find that the direct proton transfer is the preferable pathway. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

四氢叶酸辅酶结构和性能的模拟及取代一碳单元转移反应的研究

本工作模拟了四氢叶酸辅酶的结构和反应性能, 合成了模型化合物碘化1, 2-二甲基-3-对甲氧苯磺酰基咪唑啉, 研究了模型化合物与单官能团亲核体、双官能团亲核体相作用, 以甲酸、甲醛氧化态转移取代一碳单元[≡C-CH~3, =C(CH~3)CH~2NO~2]的反应, 部分反应生成了咔啉类生物碱衍生物和其它杂环类化合物。     

The Study of One Carbon Unit Transfer from Imidazolidine to dUMP Analogue with ONIOM Theory

ONIOM quantum mechanics method is used in this paper to study one-carbon unit transfer from imidazolidine to 6-aminouracil derivates. The computation results show that this reaction can be completed via three paths owing to the three different proton transfer modes. By calculation and analysis, we can find the direct proton transfer is the preferable pathway.     

One‐carbon unit transfer quantum study of 1,10‐CH+‐tetrahydroquinoxaline analog

Quantum mechanics is used in this article to study one‐carbon unit's transfer from 1,10‐tetrahydroquinoxaline analog to methylamine. The computation result shows this reaction can be completed via two paths. Each path experiences two processes of proton transferring and bond rupturing. The structures and energies of all possible stationary points have been calculated by different methods. By analyzing the result, we can find that along the reaction route the proton transfer reaction has the highest energy barrier, which indicates that a general‐acid catalysis exists in this reaction. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

N-甲基-N-丙烯醛基-甲酰氨与甲基-AICA一碳单元转移反应的量子化学研究

本文用量子化学方法研究了N-甲基-N-丙烯醛基-甲酰氨向甲基-AICA转移一碳单元的反应机理,阐明了亲核进攻和质子转移先后分步进行的反应机制。计算表明反应通道A所需的活化能较低,在竞争反应中占优势。此外,本文同时分析了甲基-AICA中C(4)上取代的甲酰胺基对该反应的影响。所有计算结果与实验结论一致。     

Quantum Chemical Study on a New Mechanism of One-carbon Unit Transfer Reaction： The Water-assisted Mechanism

It is a theoretical study on the water-assisted mechanism of one-carbon unit transfer reaction, in which the energy barrier for each transition state lowered by about 80-100 kJ/mol when compared with the one in no-water-involved mechanism. The water-assisted path 4 is the favorite reaction way. Our results well explained the presumption from experiments.     

A theoretical study on the mechanism of a novel one-carbon unit transfer reaction

The mechanism of one-carbon unit transfer reaction between tetrahydrofolate coenzymes model compound (e.g., benzimidazolium) and Grignard reagent has been investigated employing the DFT and B3LYP/6-31G* levels of theory. Three consecutive reactions leading to major products N,N′-dimethyl-ophenylenediamine and acetone have been proposed and discussed. For these reactions, the structure parameters, vibrational frequencies, and energies for each stationary point have been calculated, and the corresponding reaction mechanism has been given by the potential energy surface, which is drawn according to the relative energies. The calculated results show that the corresponding major products N,N′-dimethyl-ophenylenediamine and acetone are in agreement with experimental findings, which provided a new illustration and guidance for these reactions.     

Comparative study of folate cofactor models

The structures of a type of tetrahydrofolate cofactor models, asymmetric substituted imidazolinium, have been studied theoretically, and the relation of reactivities to the electronic structures of these compounds has been analyzed. It is found that the reactivity of one‐carbon unit transfer of this type of tetrahydrofolate cofactor models has a tight relation to properties of the two nitrogen atoms that link to the transferring carbon atom. The followed regularity is obtained. With the group on the para‐position of benzenesulfonyl changing from an electronic acceptor to an electronic donor, the difference between N3 and N6 is smaller step by step, and the model becomes more active to transfer one‐carbon unit gradually. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

适用于液晶大分子的量子化学计算方法以及六烷氧基苯并菲取代的1,3,5-三酰胺苯液晶的研究

盘状液晶分子之间的相互作用决定液晶的性质. 为了选择合适的计算方法, 以便用量子化学研究液晶大分子, 设计了对位取代苯和三酰胺苯作为模型分子, 用高水平的ONIOM [MP2/6-31G*(0.25):HF/6-31G(d,p)]计算提供了与晶体结构资料相符合的较准确的二体相互作用结果. 然后与各种较低级别的计算进行比较, 说明ONIOM (HF/STO-3G: AM1:UFF)水平比较合适. 盘重叠部分的相互作用主要是色散作用, 用UFF力场处理, 氢键主要是静电作用, 用HF/STO-3G处理, 其余部分用AM1处理. 通过对苯取代的1,3,5-三酰胺苯的双分子构型优化, 并与晶体结构数据进行比较, 进一步说明ONIOM (HF/STO-3G:AM1:UFF)水平计算的适用性. 在此基础上, 对六烷氧基苯并菲取代的1,3,5-三酰胺苯的双分子构型进行了优化, 为解释它所形成的液晶具有较高的电荷传输能力提供了有用的信息.     

3,4,4-三甲基-1-乙酰基咪唑啉盐向邻苯二胺转移一 碳单元反应的理论研究

用PM3-MO半经验方法对叶酸辅酶模型化合物3,4,4-三甲基-1-乙酰基咪唑啉盐向邻苯二胺转移一碳单元的反应进行了理论研究。结果表明,咪唑环有两种开环方式,该反应可能通过两种途径实现,每一种途径都经历了六个反应步骤,包括两次质子转移步骤,其中第二次质子转移是限速步骤。优化计算了所有步骤的中间体和过渡态的结构,各个中间体和过渡态具有不同的构型,构象和能量。     

Quantum chemical study on the thermal rearrangements of HNCRCR''''CO

MINDO/3 molecular orbital theory has been used to study the thermal rearrangements of HNCRCR'CO.The results obtained show that the activation energy of this rearrangement depends on the migrating group R and the group R'.     

Molecule dynamics and combined QM/MM study on one-carbon unit transfer reaction catalyzed by GAR transformylase

Both a molecule dynamic study and a combined quantum mechanics and molecule mechanics (QM/MM) study on Glycinamide ribonucleotide transformylase (GAR Tfase) catalytic mechanism are presented. The results indicate a direct one-carbon unit transfer process but not a stepwise mechanism in this reaction. The residues near the active center can fix the cofactor (N10-formyltetrahydrofolate) and GAR in proper relative positions by a H-bond network. The transition state and the minimum energy pathway are located on the potential energy surface. After all the residues (including H₂O molecules) are removed from the system the activation energy has increased from 145.1 kJ/mol to 243.3 kJ/mol, and the formly transfer reaction is very hard to achieve. The interactions between coenzyme, GAR and residues near the reactive center are discussed as well.     

Quantum chemical study on excited states and charge transfer of oxazolo[4,5-b]-pyridine derivatives

The excitedstate intramolecular charge transfer of four oxazolo[4,5-b]pyridine derivatives with different electron donating and electron withdrawing groups was investigated using the time-dependent density functional theory. The vertical excitation energies and the electronic structures were explored. Their distinct properties of absorption and fluorescence spectra in solvent phase were explained according to the electronic coupling matrix elements calculated by the Mulliken-Hush theory. The sub-stituent on the oxazolo[4,5-b]pyridines will remarkably change their spectra properties and increase the first excited-state dipole moments. The effect of protonation on the absorption and fluorescence spectra was also investigated systematically. Our study suggests that the present method is feasible to explain charge transfer excitation and predict the properties of absorption and emission spectra in the studied systems.     

Quantum chemical study on asymmetric catalysis reduction of imine

The asymmetric catalysis reaction is considered to be an important way by which chiral compounds are generated. Chiral 1,3,2-oxazaborolidine, as an effective asymmetric catalyst, is used widely in the enantioselective reduction of prochiral ketones, imines, and carbon-carbon double bonds[1—3]. Up to now, a number of quantum chemical modeling investigations of the en-antioselective reduction of prochiral ketones with borane catalyzed by chiral oxazaborolidines have been carried out[4—7]. Howe…     

丙烯醛光致脱羰机理的量子化学研究

用量子化学方法研究了丙烯醛基态和激发态的反应途径, 通过比较不同反应途径的反应势垒和中间产物构型的稳定性, 从理论上得出该反应的反应机理。     

生物体系中电子转移机理的研究Ⅱ: 分子间电子转移及 电子供、受体间不同基 团的影响

利用自编程序MOPAC-ET中AM1方法,及KT(Koopman'sTheorem)法,研究了二苯负离子体系的分子间电子转移现象,计算了其电子供、受体在不同距离下的V~A~B及它们之间的相关性,另外,还对两苯环间不同介入基团对电子转移的影响做了初步研究,发现不同的介入基团存在着较大的差异。