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101.
CHEN Man-Sheng DENG Yi-Fang ZHANG Chun-Hua KUANG Dai-Zhi② FENG Yong-Lan PENG Yun-Lin 《结构化学》2007,26(2):219-223
A new manganese coordination polymer 1, [Mn(H2O)4(L)]n(ClO4)2n·2nH2O·3nL (L = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene), has been synthesized and structurally characterized. The crystal structure was determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group Pn with a = 13.9176(8), b = 15.4754(9), c = 15.9670(9) , β = 99.5010(10)o, V = 3391.8(3) 3, Z = 2, C56H68Cl2MnN16O14 , Mr = 1315.10, Dc = 1.288 g/cm3, μ = 0.344 mm-1, F(000) = 1374, R = 0.0733 and wR = 0.2035. In the crystal the manganese atom is six-coordinated by two nitrogen atoms from 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and four oxygen atoms from water molecules, completing an octahedral geometry. The title complex exhibits a novel supramolecular layer architecture sustained by the concurrence of coordination bonds, hydrogen bonds, and π-π stacking interactions. 相似文献
102.
Chattopadhyay S Srivastava AK Bisaria VS 《Applied biochemistry and biotechnology》2002,102(1-6):381-393
The root explants of the germinated seedlings of Podophyllum hexandrum were grown in MS medium supplemented with indole acetic acid (IAA) (2 mg/L) and activated charcoal (0.5%), and healthy callus
culture was obtained after incubation for 3 wk at 20°C. The cultivation of plant cells in shake flask was associated with
problems such as clumping of cells and browning of media, which were solved by the addition of pectinase and polyvinylpyrrolidone.
The effect of major media components and carbon source was studied on the growth and podophyllotoxin production in suspension
culture. It was found that glucose was a better carbon source than sucrose and that NH4
+:NO3
− ratio (total nitrogen concentration of 60 mM) and PO4
3− did not have much effect on the growth and product formation. The relative effect of culture parameters (inoculum level,
pH, IAA, glucose, NH4
+:NO3
− ratio, and PO4
3−) on the overall growth and product response of the plant cell suspension culture was further investigated by Plackett-Burman
design. This indicated that inoculum level, glucose, IAA, and pH had significant effects on growth and production of podophyllotoxin.
To identify the exact optimum concentrations of these parameters on culture growth and podophyllotoxin production, central
composite design experiments were formulated. The overall response equations with respect to growth and podophyllotoxin production
as a function of these culture parameters were developed and used to determine the optimum concentrations of these parameters,
which were pH 6.0, 1.25 mg/L of IAA, 72 g/L of glucose, and inoculum level of 8 g/L. 相似文献
103.
Antonio García Martínez Santiago de la Moya Cerero Beatriz Lora Maroto 《Tetrahedron》2005,61(12):3055-3064
An empiric first approach to the knowledge about the structural factors influencing the catalytic behavior of conformationally flexible δ-amino-alcohol-based ligands, for the enantioselective addition of dialkylzincs to prochiral carbonyl groups, has been applied using the 1-(2-aminoethyl)norbornan-2-ol moiety as the model chiral system, and the asymmetrically catalyzed addition of diethylzinc to benzaldehyde as the test reaction. For this purpose, a selected small library of seven norbornane-based chiral ligands, bearing well-defined structural variations to allow a comparative study, that is, variation of the relative configuration and steric hindrance at the C(2), C(3) and/or C(7) norbornane positions, has been synthesized and probed in the mentioned test reaction. The experimental results obtained have been rationalized empirically using diastereomeric Noyori-like transition states, demonstrating that the conformational flexibility of the δ-amino-alcohol ligands, contrary to the more studied and rigid β-amino-alcohols, plays a crucial role on the catalytic behavior of such ligands (stereochemical sense and degree of the stereodifferentiation in the asymmetric process), which makes such structural factors, important for the improved design of new related chiral catalysts. In this sense, a robust crude empirical model for the prediction of the catalytic behavior of such δ-amino-alcohol-based ligands is proposed. 相似文献
104.
105.
Huwe A Mazitschek R Giannis A 《Angewandte Chemie (International ed. in English)》2003,42(19):2122-2138
Cell division (mitosis) is one of the basic requirements for multicellular oranisms. The capability of a cell to replicate enables a complex assembly to be created. Faulty regulation of the control mechanism in the cell cycle leads to an excessive cell proliferation and is the cause of cancer. The key position of the cyclin-dependent kinases (CDKs) and their direct partners, as well as the fact that the majority of malign illnesses show defects in at least one of these key players of the cell cycle, is of great interest for the development of low-molecular-weight CDK inhibitors. In this Review an overview of the different structural classes of ATP-competitive inhibitors of CDKs are given, whose devlopment was aimed at battling cancer. The Review shows how far the development of selective CDK inhibitors has progressed and to what extent the expectations for such drugs have so far been fulfilled. 相似文献
106.
An experimental mixture design was applied to a differential scanning calorimetry (DSC) study performed to evaluate naproxen
compatibility in tablet formulations consisting of four classic excipients (sorbitol, sodium carboxymethylcellulose, poly(ethylene
glycol) 20000 and Veegum) each in adequate concentration ranges accounting for the relevant values actually used in pharmaceutical
formulations. Twenty-seven different tablets were obtained from as many mixtures prepared according to the experimental design
plan and analyzed in a random order by DSC. Statistical evaluation of experimental data enabled correlation of both enthalpy
and onset temperature variations of drug melting endotherm (selected as responses indicative of the presence of drug-excipient
interactions) with the mixture composition. Variance analysis (Anova) confirmed the reliability of the postulated polynomial
model in providing adequate prediction of true system behaviour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
107.
108.
One of the major techniques used for the method development of ternary and quaternary high performance liquid chromatography (HPLC) systems has been to use mixture designs, often referred to as "Glajch's Triangle". This technique does not allow for the systematic and simultaneous optimization of other factors such as gradient time, pH and temperature that affect the quality of separations. An alternative approach is to use experimental designs. The condition, however, that the composition of all components of the mobile phase must total 100% presents a problem when trying to mathematically represent ranges of each mobile phase constituent of a ternary or quaternary system. A method is described here, based on spherical coordinate representations, that adheres to the constraints of the mobile phase composition and allows experimental designs, such as central composite and factorial designs, to be applied to the simultaneous optimization of the mobile phase composition. Other factors, in particular temperature and gradient time, can then be included in the design. As a result of applying these designs to the HPLC separation of phenols and corticosteroids, it was found necessary to include three-way interactions between experimental factors in the model. The significance of these interactions shows that they need to be considered in HPLC method development. 相似文献
109.
Summary In this paper an application is presented of the median molecule workflow to the de novo design of novel molecular entities with a property profile of interest. Median molecules are structures that are optimised to be similar to a set of existing molecules of interest as an approach for lead exploration and hopping. An overview of this workflow is provided together with an example of an instance using the similarity to camphor and menthol as objectives. The methodology of the experiments is defined and the workflow is applied to designing novel molecules for two physical property datasets: mean molecular polarisability and aqueous solubility. This paper concludes with a discussion of the characteristics of this method. 相似文献
110.
A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex (Fig. 4b) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate. 相似文献