西加毒素(CTX)的电子结构及构效关系研究

应用ＭＮＤＯ方法对ＣＴＸ衍生物进行了量子化学计算,得到了它们的电子结构信息,根据构象分析研究了它们的空间结构,推测出它们的活性部位,探讨了与受体结合时的作用方式,讨论了结构－活性关系,解释了活性差异的原因,研究结果表明该类化合物的Ｄ、Ｅ、Ｆ环和Ａ环及其支链等部位的不饱和键对活性有重要影响。     

微型氧弹热量计和C60及C70的燃烧焓

富勒烯是新发现的一类碳的稳定单质，其分子骨架中含有多个五员环及非平面球壳状大力键.与全为六员环的平面大r键的石墨结构相比，这些张力提高了分子能量.通过富勒烯的生成焰的测定，对了解这些分子的稳定性和反应性，它们的生成机理，以及研究分子的结构与能量的规律是很有意     

多蝶烯及其衍生物的合成与应用进展

多蝶烯及其衍生物是一类具有独特三维刚性结构的芳香族化合物,它们由三个以上的独立苯环连接在 双环辛三烯片段上而形成,多蝶烯的概念是对三蝶烯概念的扩展。近年来,由于其特殊的刚性、芳香性以及三维骨架结构,该类化合物引起了人们越来越多的关注,并在超分子化学、材料化学、分子机器等许多领域得到了越来越广泛的应用。本文首先概述多蝶烯、多蝶烯醌及其衍生物的合成,然后重点介绍多蝶烯衍生物在共轭聚合物材料、有机多孔与低介电常数材料、化学传感、单层自组装结构、分子机器以及基于新型合成主体超分子化学等方面的应用研究进展。     

穿心莲内酯抗肿瘤作用衍生物的合成研究进展

作为爵床科植物穿心莲的主要活性成分之一,穿心莲内酯具有广泛的药理活性.近年来,已有大量研究表明对穿心莲内酯进行结构改造可提升其抗肿瘤作用.因此,根据穿心莲内酯衍生物结构特点,将其按照基础骨架不同分为五类,分别为穿心莲内酯骨架衍生物、14-去氧穿心莲内酯骨架衍生物、脱水穿心莲内酯骨架衍生物、异穿心莲内酯骨架衍生物以及12-环替代的穿心莲内酯骨架衍生物.在此基础上,对穿心莲内酯衍生物的合成以及抗肿瘤活性结果进行综述,并初步总结其构效关系.最后,对衍生物未来的研究趋势进行了展望.     

宝塔烷电子结构与张力的ab initio研究

利用MNDO程序优化出宝塔烷、宝塔烷双正离子及宝塔二烯的构型参数。从头算的电荷分布及分子轨道均表明: 宝塔烷与其价键异构体宝塔二烯性质相近。双正离子的中间四个碳原子则形成了一种与环丁烷双正离子类似的四中心双电子大π键。张力研究表明, 宝塔烷的键张力要比不能稳定存在的小螺桨烷小得多, 说明了宝塔烷骨架的刚性及稳定性。     

鬼臼毒素衍生物的量子化学研究

对若干个鬼臼毒素衍生物进行了量子化学计算,根据其电子结构及有关分析结果,结合它们对体外L1210白血病细胞生长的抑制活性(IC50),讨论了它们的活性部位及构效关系,发现具有较高活性的化合物分子中有三个重要部位：C4位为有效的修饰位点;B环及E环是重要的活性部位,其中B环是接受电子的主要活性部位,其正电性越高,活性越强;E环及其4'位酚羟基氧的负电性越高,活性越强。     

1. 5-环辛二烯-3, 7-二炔(C~8H~4)结构和光谱性质的理论研究

采用量子化学从头算方法研究了1,5-环辛二烯-3,7-二炔(C~8H~4)的结构和光谱性质,根据等键反应分析和自然键轨道方法研究了它的稳定性、成键情况和共轭性。结果表明1,5-环辛二烯-3,7-二炔(C~8H~4)分子为平面刚性结构,可能稳定存在。分子中C≡C键与C=C键存在一定程度的共轭,可能具有芳香性。     

1,6-环十二二烯-2,4,8,10四炔的结构和光谱的从头算研究

用量子化学从头计算方法对１,６－环十二二烯－２,４,８,１０四炔的几何结构和光谱性质进行了研究,在优先分子构型的基础上通过等键反应分析分析和自然键轨道方法研究了它的稳定性、成键情况和共轭性。结果表明,１,６－环十二二烯－２,４,８,１０四炔是一个平面刚性分子,具有一定程度的稳定性,可能稳定存在。分子中的Ｃ≡Ｃ键与Ｃ＝Ｃ键,Ｃ≡Ｃ键与Ｃ≡Ｃ健存在一定程度的共轭,分子可能具有芳香性。     

西加毒素(CTX)的电子结构及构效关系研究

应用MNDO方法对CTX衍生物进行了量子化学计算 ,得到了它们的电子结构信息.根据构象分析研究了它们的空间结构.推测出它们的活性部位 ,探讨了与受体结合时的作用方式 ,讨论了结构 -活性关系 ,解释了活性差异的原因.研究结果表明该类化合物的D、E、F环和A环及其支链等部位的不饱和键对活性有重要影响     

三环系环庚富烯衍生物的合成

环庚富烯是一种交替共轭的极不稳定的化合物，但Ｃ８位带有强吸电子取代基的环庚富烯衍生物是相当稳定的，如８，８－二氰基环庚富烯（１）［１］Ｘ－射线晶体结构分析数据表明，１具有接近平面的结构，其环外双键的键长为１．４２Ａ，已显示部分双键的性质［２］。这一结果表明，吸电子的氰基的引入，增加了对偶极结构（１ｄ）的贡献，使分子趋于稳定。我们合成了一系列二环系五员杂环并环庚富烯衍生物（２），用可变温核磁共振线状分析技术，证实了１０π体系的电子离域可加大偶极结构的贡献，降低环庚富烯环外双键的旋转能垒［３］。为了…     

Solution conformation by NMR and molecular modeling of three sulfide-free somatostatin octapeptide analogs compared to angiopeptin

Summary The conformation in dimethylsulfoxide of the somatostatin derivative angiopeptin and of three disulfide-free analogs was estimated by two-dimensional nuclear magnetic resonance spectroscopy at room temperature. The resulting 3D molecular graphics were compared and shown to reflect the observed differences in the inhibition of restenosis after rat aorta balloon injury by these octapeptide inhibitors. Angiopeptin and its active analog 2 displayed a relatively rigid conformation of the cyclic hexapeptide backbone due to the presence of two well-defined hydrogen bonds, further stabilized by a third hydrogen bond outside the ring. No such constraints were detected for the two biologically inactive analogs, which, compared to 2, had a two-atom longer or shorter hexapeptide ring. The well-defined structure of compound 2 may serve as an improved pharmacophore for this new class of drugs.     

丁吡吗啉与其苯基类似物的电子结构特征比较

通过化学合成获得丁吡吗啉及其苯基类似物,并对其杀菌活性进行了比较.借助X射线晶体衍射方法,对丁吡吗啉的结构进行了解析.进一步选择6-31G(2df,2pd)基组,利用密度泛函理论B3LYP方法对丁吡吗啉及其苯基类似物的空间几何结构进行优化,借助前线分子轨道、Mulliken电荷、自然键轨道(NBO)分析、表观静电势等对丁吡吗啉及其苯基类似物的电子结构与其杀菌活性相关性进行了理论探讨.结果表明吡啶环取代苯环后,一方面吡啶环上的N原子是一个负电中心,有利于与受体分子间形成氢键等相互作用;另一方面,吡啶环又是一个缺电子的芳环,与苯环相比,在与受体的π-π相互作用中能起到更好的电子接受体的作用.这两种因素使得丁吡吗啉更容易与受体结合,因而活性更高.     

Antiangiogenic Activity and in Silico Cereblon Binding Analysis of Novel Thalidomide Analogs

Due to its antiangiogenic and anti-immunomodulatory activity, thalidomide continues to be of clinical interest despite its teratogenic actions, and efforts to synthesize safer, clinically active thalidomide analogs are continually underway. In this study, a cohort of 27 chemically diverse thalidomide analogs was evaluated for antiangiogenic activity in an ex vivo rat aorta ring assay. The protein cereblon has been identified as the target for thalidomide, and in silico pharmacophore analysis and molecular docking with a crystal structure of human cereblon were used to investigate the cereblon binding abilities of the thalidomide analogs. The results suggest that not all antiangiogenic thalidomide analogs can bind cereblon, and multiple targets and mechanisms of action may be involved.     

The molecular structure of N-benzylidene-aniline

The molecular structure of N-benzylidene-aniline has been studied experimentally by the gas electron diffraction method, and also by molecular mechanics calculations. Both approaches gave the same results for the most stable conformer of the free molecule. The phenyl ring bonded to the carbon end of the CN bond was found to be coplanar with this bond, while the other phenyl ring was extensively (ca. 52°) rotated about the NΦ bond.     

Visualization and quantification of the anisotropic effect of C=C double bonds on 1H NMR spectra of highly congested hydrocarbons-indirect estimates of steric strain

The anisotropic effect of the olefinic C=C double bond has been calculated by employing the NICS ( nucleus independent chemical shift) concept and visualized as an anisotropic cone by a through space NMR shielding grid. Sign and size of this spatial effect on (1)H chemical shifts of protons in norbornene, exo- and endo-2-methylnorbornenes, and in three highly congested tetracyclic norbornene analogs have been compared with the experimental (1)H NMR spectra as far as published. (1)H NMR spectra have also been calculated at the HF/6-31G* level of theory to get a full, comparable set of proton chemical shifts. Differences between delta( (1)H)/ppm and the calculated anisotropic effect of the CC double bond are discussed in terms of the steric compression that occurs in the compounds studied.     

The nature of sulfur bonding in thiopyrylium cation

Comparison of the PMR spectrum ofthiopyrylium cation with those of the oxygen (pyrylium cation) and nitrogen (pyridinium cation) analogs has suggested the unique electronic structure of the thiopyrylium cation. To investigate this structure the extended Hückel MO calculations have been carried out using two basis sets, one with and another without sulfur 3d orbitals. The electronic structure of thiopyrylium cation can be rationalized by the 3d orbital involvement of the S atom in the basis set. The primary effect of the involvement of 3d orbitals on the S atom is shown to be the electron transfer from the ring carbon fragment, in particular from the β ring carbons, to the S atom, with an accompanying increase in sulfur-α-carbon bond order.     

X-ray Crystal Structure and Molecular Mechanics Calculations of (2,6-iso-dipropyl-phenylamide) Dimethyl ( tetra-methylcyclopenta-dienyl ) Silane Titanium Dichloride

Crystal and molecular structure of (2,6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic, with a = 12.658 (3) (A), b = 16.62 (3)(A), c = 11.760 (2)(A), V = 2474.2 (9)(A) 3, Z = 4, space group Pnma, R = 0.0399. Componud I compose of the π-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed.     

X-ray Crystal Structure and Molecular Mechanics Calculations of (2,6-iso-dipropyl-phcnylamidc) Dimethyl (tetra-methylecyclopenta- dienyl)Silane Titanium Dichloride

ExperimentalSynthesisofitToI.sg(4mmol.)TiCI,.THFin25mLTHFwasaddedI.sg(4mmol.)dilithium(2,6-propylphenylamide)dimethyl(tetra-methylcyclopentadienyl)silaneandthemixturewasallowedtostirforIhour,then0.639AgCI(4mmol.)wasadded.After4hoursstirring,thesolventwasmovedandtheresiduewasextractedwithdiethylether.Theetherextractwasfilteredandevaporatedtodrynesstogive0.409yellowcrystallinesolid,yield41%.'H-NMR(C,D,)f0.48(6H),l.I2(6H),l.49(6H),l.98(6H).2.18(6H),and3.04(2H).Asuitablesinglecrystalwa…