Persistent carbocations from 4,4′-dimethylaminodiphenylethylenes within CaY zeolite: intrazeolite-water controls the structure of the carbocation

Inclusion of 4,4′-dimethylaminodiphenylethylene and related olefins within activated CaY results in the formation of persistent monomer carbocations. The structure of the cation, consequently the color of the zeolite, is controlled by water molecules present within zeolites. Under ‘dry’ conditions the zeolite is light yellow and under ‘wet’ conditions it is blue colored. Blue color results from the quininoidal structure adopted by 1,1-bis-(4-dimethylaminophenyl)ethyl cation through participation of the lone pair electrons present on the amino substituent at the para position.     

Quantum chemical studies of peptide nucleic acid monomers and role of cyclohexyl modification on backbone flexibility

Peptide nucleic acids (PNA) bind sequence specifically to DNA/RNA and are of major interest for all fields of molecular biology and could form the basis for gene‐targeted drugs. Modifications are introduced in PNA to overcome problems associated with orientational selectivity in binding, to restrict conformational flexibility of backbone, and to discriminate binding for either DNA or RNA. The addition of geometrical isomers (1R,2S and 1S,2R) of cyclohexyl ring in the backbone of PNA could bring rigidification to PNA backbone and may impart specificity toward RNA. Therefore, quantum chemical studies are aimed to explore the conformational space, to find out preferred stable conformations of PNA and modified (1R,2S and 1S,2R) cyclohexyl PNA monomer. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

(4R,4aR,6S,7S,7aS)‐6‐Hydro­xy‐7‐hy­droxy­methyl‐4‐methyl­per­hydro­cyclo­penta­[c]­pyran‐1‐one chloro­form solvate from Valeriana laxiflora

The structure of an iridolactone isolated from Valeriana laxiflora was established as (4R,4aR,6S,7S,7aS)‐6‐hydroxy‐7‐hydroxy­methyl‐4‐methyl­per­hydro­cyclo­penta­[c]­pyran‐1‐one chloro­form solvate, C₁₀H₁₆O₄·CHCl₃. The two rings are cis‐fused. The δ‐lactone ring adopts a slightly twisted half‐chair conformation with approximate planarity of the lactone group and the cyclo­pentane ring adopts an envelope conformation. The hydroxy group, the hydroxymethyl group and the methyl group all have β orientations. The absolute configuration was determined using anomalous dispersion data enhanced by the adventitious inclusion of a chloro­form solvent mol­ecule. Hydro­gen bonding, crystal packing and ring conformations are discussed in detail.     

Complementary stereoselective conjugate addition reactions on indolo[2,3-a]quinolizine templates

We report a new and highly stereoselective approach for the construction of a range of functionalized indolo[2,3-a]quinolizine targets from a readily available, nonracemic chiral template. The methods developed allow us to predetermine relative product stereochemistries by judicious choice of substrate sub-structure.     

Determination of 3-hydroxy pterocarpan, a novel osteogenic compound in rat plasma by liquid chromatography-tandem mass spectrometry: application to pharmacokinetics study

A rapid, sensitive and selective LC‐MS/MS method for the quantitative analysis of 3‐hydroxy pterocarpan (S006‐1709) in female rat plasma has been developed and validated. A Discovery RP₁₈ column was used for the chromatographic elution using acetonitrile and 0.1% acetic acid in water as mobile phase (80:20 v/v) at the flow rate of 0.5 mL/min. MS/MS analysis was performed using a triple quadrupole mass spectrometer with electrospray ionization in negative ion mode using biochanin as an internal standard (IS). Extraction of S006‐1709 and IS from rat plasma was done by liquid–liquid extraction method using diethyl ether. The LC‐MS/MS method was sensitive with 1.95 ng/mL as the limit of detection and 3.9 ng/mL as the lower limit of quantification. The method was linear in the concentration range of 3.9–1000 ng/mL. The percentage bias for intraday and interday accuracy was not greater than 4.2 and the %RSD for intraday and interday precision was not greater than 13.2. The recoveries of S006‐1709 and IS were 73.9–79.3 and 85.7%, respectively. S006‐1709 was found to be stable in various stability studies. The validated LC‐MS/MS method was successfully applied for the oral pharmacokinetics study of S006‐1709 at 10 mg/kg in female Sprague–Dawley rats. Copyright © 2010 John Wiley & Sons, Ltd.     

On the formation of amorphous layers by interdiffusion in zirconium-copper system

Formation of amorphous phase by solid state reaction has been observed in bulk copper-zirconium couples. Transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and differential scanning calorimetry (DSC) techniques have been employed to detect and study the amorphous phase. The experimental observations have been explained with a model, which considers the breakdown of the a-zirconium lattice due to the solute enrichment beyond a certain limit where the nucleation of the amorphous phase becomes thermodynamically possible. The present-experiments convincingly show that amorphous phase can form in bulk diffusion couples made from large-grained well-annealed material and conclusively establish that the presence of crystal defects in high concentrations is not a pre-requisite for the formation of amorphous phase.     

Electronic structure of hafnium: A compton profile study

In this paper, we report the first-ever isotropic Compton profile of hafnium measured at an intermediate resolution, with 661.65 keV γ-radiation. To compare our experimental data, the theoretical computations have also been carried out within the framework of pseudopotential using CRYSTAL03 code and the renormalized-free-atom (RFA) model. It is found that the present experimental profile is in better agreement with the RFA calculations if the outer electronic configuration is chosen as 5d^3.26s^0.8. The cohesive energy of Hf is also deduced from the experimental data and is compared with the available data. On leave from Hindu College, Sonepat 131 001, India     

腙基席夫碱配体铜(Ⅱ)配合物的合成、结构表征、生物活性和密度泛函理论计算

以甲醇为介质,合成了3种新的席夫碱配体HL¹(2-hydroxybenzaldehyde2-(2-oxo-1,2-diphenylethylidene)hydrazone)、HL²(4-hydroxybenzaldehyde2 -(2 - oxo- 1,2 -diphenylethylidene)hydrazone)和 L³(2 -methoxybenzaldehyde2-(2-oxo-1,2-diphenylethylidene)hydrazone)的Cu(Ⅱ)配合物1~3。通过元素分析、光谱方法、磁化率测量和密度泛函理论(DFT)计算对配合物进行了表征。通过单晶X射线衍射研究对合成的配体进行了结构表征。通过DFT计算确定了配合物的优化结构。通过紫外可见吸收光谱和荧光发射光谱研究了配合物与小牛胸腺DNA(CT-DNA)的结合能力。吸收光谱研究揭示了增色效应,并提出了与CT-DNA相互作用的可能模式。溴化乙锭(EB)竞争结合研究表明,配合物可以取代 DNA-EB 加合物中的 DNA,且配合物可能以嵌入模式与 CT-DNA结合。配合物对革兰氏阴性肺炎克雷伯菌、大肠杆菌、鲍氏志贺菌和革兰氏阳性金黄色葡萄球菌的体外抗菌活性研究表明,配合物2对肺炎克雷伯菌和鲍氏志贺菌具有明显抗菌活性,但配合物1和3没有表现出任何显著的抗菌活性。     

Suzuki-Miyaura reactions of N-protected tribromopyrazoles. Efficient and site-selective synthesis of 3,4,5-triaryl-pyrazoles, 3,5-diaryl-4-bromopyrazoles and 5-aryl-3,4-dibromopyrazoles

Suzuki-Miyaura reactions of N-protected tribromopyrazoles were studied. The reactions proceed with excellent site-selectivity. The first attack occurs at position 5, while the second and third attack occur at positions 3 and 4, respectively. A variety of 3,4,5-triaryl-pyrazoles, 3,5-diaryl-4-bromopyrazoles, and 5-aryl-3,4-dibromopyrazoles were efficiently prepared. The products are not readily available by other methods.