甲酰基硫脲类嘧啶衍生物结构与活性的理论研究

硫脲类化合物是一类具有广泛抗菌和杀菌活性的物质。为了揭示此类化合物结构与活性之间的关系，为新型杀菌剂的制备和筛选提供理论依据，本文运用Gaussian03程序，在6—311G基组水平上用DFT—B3LYP方法对6种甲酰基硫脲嘧啶衍生物进行研究，对6种化合物的几何构型进行了优化，得到了键长、键角、二面角、原子净电荷等优化几何参数以及分子轨道能量参数。根据优化结果分析了6种化合物的结构特点以及结构和活性之间的关系。计算了6种化合物的红外光谱性质，并且将红外光谱的计算数据和实验数据做了比较。对化合物进行结构分析和红外光谱分析的结果表明：（1）嘧啶环与C（1）-N（7）键形成的共轭基团以及N（9）上的负电荷越多，化合物的活性越高；（2）计算结果与实验结果相吻合，很好地反映了甲酰基硫脲类嘧啶衍生物化合物结构-活性关系。证明DFT-B3LYP／6—311G是一种很好的研究此类化合物结构-活性关系的量子化学方法；（3）本研究为新型酰基硫脲类杀菌剂的开发研究提供了理论依据和研究方法。

Theoretical studies on the structure-activity relationship of N'-( substituted pyrimidin-2-yl)-N-substituted formyl thioureas

Thioureas as a kind of highly active bactericides have been broadly studied for many years. Many novel substituted thioureas were synthesized in recent years. But there is still no clear theoretical explanation about the active mechanism of these compounds. In order to discover the relationship between these compounds' structures and their activities,the calculations on six N'-( substituted pyri-midin-2-yl)-N-substituted formyl thioureas were carried out using DFT-B3LYP method at 6-311G basis set in Gaussian03 package. Geometric structures of the six compounds were optimized. Optimized parameters (bond distances, bond angles, dihedrals, atomic net charges) and orbital energies were obtained. Moreover, the structural characters and the relationship between the structures and activities of these compounds were analyzed according to the optimized results. Infrared Spectrums of the six compounds were calculated. From the analysis on the optimized structures and the IR frequencies, we concluded that: (1) The more negative charges on N ( 9) and the conjugate radicle formed by pyrimidine ring and C(1) -C(7) bond, more active the compound will be. ; (2) The calculated data showed a good agreement with the experimental results which demonstrated the structure-activity relationship of the studied compounds correctly. So DFT-B3LYP is a feasible quantum method to study N'-(substituted pyrimidin-2-yl)-N-substituted formyl thioureas; (3) The research provides theoretical backgrounds and good quantum method for the further study of new acyl thiourea bactericides.