Cis‐trans Isomerism in Copper(II) Complexes with N‐acyl Thiourea Ligands

The N‐acyl thiourea complexes bis[N,N‐diethyl‐N′‐(p‐nitrobenzoyl)‐thioureato]copper(II) ( 1a,1b ) and bis(N,N‐diphenyl‐N′‐benzoylthioureato)copper(II) ( 2a,2b ) crystallize in each case in two modifications. X‐ray structural analysis shows that 1a and 1b are cis‐trans isomers. This is very unusual for N‐acyl thioureato complexes because with exception of one platinum(II) complex up to now only cis complexes have been found. In contrast X‐ray structural analysis of both forms 2a and 2b of the other complex shows no cis‐trans pair. Both modifications are cis complexes. In solution both isomers of the copper(II) complexes are observable by EPR spectroscopy.     

Synthesis and conformational behavior of pseudopeptides containing δ-azaproline. A cis conformational preference for Xaa1–δ-azaPro bond

δ-Azaproline, a new bis-nitrogen proline surrogate has been used in order to control the conformation of an AA–ΨPro bond. Conformational analysis of Xaa₁–δ-azaPro–Xaa₃ performed by NMR, IR experiments, and molecular modeling revealed a preference for a trans conformation of the Xaa₁–δ-azaPro bond when δ-azaPro is protected by a Boc group. The removal of the Boc protection leads to the establishment of a C₁₀ pseudocycle via a hydrogen bond network favoring the cis conformation of the Xaa₁–δ-azaPro bond.     

The Studies of 13C NMR Chemical Shifts and Induced Lanthanide Shift Reagent Cis-trans Isomerization of N-Cinamylidene-hexyl,t-butyl and Substituted Aryl-Amines

The Carbon-13 chemical shifts of N-Cinamylidenehexyl, t-butyl and sixteen substituted aryl amines were analysed. The lanthanide induced carbon-13 chemical shifts of the cis and trans of four N-cinamylidene substituted anilines were analysed. The spectra N-cinamylidene hexylamine showed only the trans form. The cis/trans ratio of N-cinamylidene aryl amines increased as the LSR concentration increased.     

Synthesis of rigid photoswitchable hemithioindigo ω-amino acids

The synthesis of novel N-Boc- and N-Fmoc protected hemithioindigo-based ω-amino acids is described. An approach to modulate the thermal stability of a hemithioindigo subunit is presented. Placing the amino-group in the stilbene part from the para- to meta-position leads to an increase of the half-life of the thermally labile E-form from 19 h to 47 h.     

Biaxial ordering of terminal diene groups in lipid membranes: an infrared linear dichroism study

The molecular order within the hydrophobic core of membranes of the diene lipid di-tetradecadienoylphosphatidylcholine was studied by means of infrared spectroscopy on multibilayer assemblies which orient macroscopically on the surface of an attenuated total reflection crystal. The relative humidity and temperature were used as variable parameters to demonstrate that there were profound differences in the melting transition of lipids possessing predominantly cis and trans diene groups. The cis isomer undergoes the phase transition at a vapor pressure which is increased by 0.15 GPa when compared with that of the trans isomer. The methylene wagging band progression gives no indication of differences between the acyl chain conformation of the cis and trans forms in the gel state. The frequencies of a number of absorption bands of the diene groups reveal that these moieties are predominantly in the s-trans conformation to accommodate a favorable packing within the bilayer. The linear dichroism of selected in-plane and out-of-plane vibrations of the diene groups gives indications of the biaxial ordering of these moieties. We present the basic equations for the quantitative analysis of IR dichroism data of lamellar structures in terms of transverse and longitudinal molecular order parameters. It turns out that the planes of the rigid diene groups orient preferentially in a perpendicular direction with respect to the bilayer surface and parallel to each other forming in this way a layer of well-aligned diene groups in the bilayer center. This finding is confirmed by the results of X-ray measurements. We suggest that the partial interdigitation of the diene groups of the sn-1 acyl chains promotes the formation of the inverse H_II phase and/or enables the formation of covalent bonds between both the monolayers upon polymerization of diene lipids.     

Regioselective Synthesis of Fatty Acid Esters of Glycosides Containing Cis‐diol and Biological Test against Bacterial Staphylococcus aureus and Salmonella agona

Regioselectivity of glycoside containing cis‐diol esterification with fatty acid using dibutyltin dimethoxide as stannylating agent was probed, the results showed the equatorial position of cis‐diol has some advantage of being acylated, although the orientation of adjacent groups could affected the regioselectivity. The glycoside fatty acid esters were regioselectively synthesized on optimized condition with this stannyl method, the biological tests against bacterial as Staphylococcus aureus and Salmonella agona were carried out with these fatty acid esters, the testing results showed that glycoside esters with 12 or 14 carbon long chain fatty acid have some obvious inhibition against Staphylococcus aureus.     

二氯菊酸类杀虫剂光学纯度分析方法的研究

报道了旋光性的顺式－2，2－二甲基－3－（2，2－二氯乙烯基）环丙烷羧酸（谷称顺式二氯菊酸）类杀虫剂光学纯度的色谱分析方法。光学活性杀虫剂的顺式－2，2－二甲基－3－（2，2－二氯乙烯基）环丙烷羧酸先与氯化亚砜生成酰氯，一财与S（－）－a-甲基苄胺作用，生成顺式－2，2－二氯－3－异丁烯基环丙烷羧酸非对映异构体的酰胺，经薄层色谱纯，用高效液相色谱进行分析，即可确定中间体的光学纯度。光学纯度一定的中间体经合成至最终产物，其光学纯度保持不变。     

偶氮苯聚合物5-NO2-PADAT及其与Pd(Ⅱ)的螯合物光存储特性

本文制备了偶氮苯聚合物5-NO₂-PADAT和它与Pd(Ⅱ)形成的螯合物,用简并四波混频的方法测量了它们的三阶非线性系数及光存储特性,通过对测量结果的分析,得到了光束在信号写入与读取过程中的关系。     

Synthesis of novel biscrown ethers with rigid cis/trans ethylene bridge

Two novel biscrown ethers with rigid cis/trans ethylene linker were synthesized via Wittig reaction in high yield （about 80%）. Their pure cisltrans-isomers were obtained by column chromatography separation. And their structure/configuration was confirmed by ^1H NMR,^ 13C NMR, ESI mass spectrum, elemental analysis and UV-vis speca＇a.     

Proton and Carbon - 13 NMR Assignments for Fluorinated and Nonfluorinated Aromatic Ketimines

The ¹H and ¹³C NMR spectra of three aromatic ketimines with varying degrees of fluoro substitution have been extensively studied using one and two dimensional techniques. COSY experiments were conducted to identify the protons on each of the aromatic groups, HETCORR experiments were then utilized to identify the corresponding carbon atoms, and then the order of the carbon atoms was established by long-range HETCORR (HRTCORRLR) results. These studies have allowed rigorous assignments to be made for most of the carbon and hydrogen atoms present in these compounds. Fluorine splittings were very helpful in the analyses. In the course of this study, the NMR absorbances (¹H and ¹³C) of related aldimines have also been assigned. This constitutes the first report on the assignments of ¹H and ¹³C absorbances for ketimines. The observed spectral properties suggest that the structure of aromatic ketimines is one in which the aromatic rings are in three different planes. Two of the aromatic rings, the N-substituted ring and the C-substituted ring in the cis configuration, are twisted substantially out of the plane with respect to the -C=N- bond. The remaining C-substituted aromatic ring, trans to the N-substituted ring, lies in the deshielding zone of the imine bond.