Studies on annelation of (+)-2-caranone

Summary The Michael reaction of (+)-2-caranone (1) with methyl vinyl ketone, ethyl vinyl ketone or methyl acrylate was utilized for synthesis of corresponding diketones4 and5 and keto ester8. These compounds were subjected to cyclization to obtain the sesquiterpenoid systems.

---

Untersuchungen über die Annelierung von (+)-2-Karanon

Zusammenfassung Die Michaelreaktion von (+)-2-Karanon mit Methylvinylketon, Ethylvinylketon oder Methylakrylat wurde zur Synthese der entsprechenden Diketone4 und5 und des Ketoesters8 genutzt. Diese Verbindungen wurden weiterhin einer Zyklisierung unterworfen, um zu Sesquiterpenoidstrukturen zu gelangen.

     

Lipophilicity of a series of 1,2-benzisothiazol-3(2H)-ones determined by reversed-phase thin-layer chromatography

A reversed-phase high-performance liquid chromatographic method with detection at 220 nm was developed and validated for the determination of ethyl-3-(N-n-butyl-N-acetyl)aminopropionate, IR 3535, in an insect repellent semi-solid product. A Hypersil ODS RP-C18 column (250 x 4.6 mm), 5 microm particle size, was equilibrated with a mobile phase consisted of water-acetonitrile (60:40, v/v). Its flow-rate was 1.0 ml/min. Excipients did not interfere with the determination of IR 3535 (Rs = 8.663). Intra- and inter-day relative standard deviations for samples were not higher than 0.61 and 1.2%, respectively. Mean recovery was found not lower than 98.5% and not higher than 100.3%. The method of external standard was adopted. Calibration curves were linear in the concentration range between 1.0 x 10(-6) and 5.0 x 10(-4) M. Limits of detection and quantitation were 65 and 196 ng/ml, respectively.     

Molecular modeling of the human vasopressin V2 receptor/agonist complex

The V2 vasopressin renal receptor (V2R), which controls antidiuresis in mammals, is a member of the large family of heptahelical transmembrane (7TM) G protein-coupled receptors (GPCRs). Using the automated GPCR modeling facility available via Internet (http://expasy.hcuge.ch/swissmod/SWISS-MODEL.html) for construction of the 7TM domain in accord with the bovine rhodopsin (RD) footprint, and the SYBYL software for addition of the intra- and extracellular domains, the human V2R was modeled. The structure was further refined and its conformational variability tested by the use of a version of the Constrained Simulated Annealing (CSA) protocol developed in this laboratory. An inspection of the resulting structure reveals that the V2R (likewise any GPCR modeled this way) is much thicker and accordingly forms a more spacious TM cavity than most of the hitherto modeled GPCR constructs do, typically based on the structure of bacteriorhodopsin (BRD). Moreover, in this model the 7TM helices are arranged differently than they are in any BRD-based model. Thus, the topology and geometry of the TM cavity, potentially capable of receiving ligands, is in this model quite different than it is in the earlier models. In the subsequent step, two ligands, the native [arginine⁸]vasopressin (AVP) and the selective agonist [d-arginine⁸]vasopressin (DAVP) were inserted, each in two topologically non-equivalent ways, into the TM cavity and the resulting structures were equilibrated and their conformational variabilities tested using CSA as above. The best docking was selected and justified upon consideration of ligand-receptor interactions and structure-activity data. Finally, the amino acid residues were indicated, mainly in TM helices 3-7, as potentially important in both AVP and DAVP docking. Among those Cys¹¹², Val¹¹⁵-Lys¹¹⁶, Gln¹¹⁹, Met¹²³ in helix 3; Glu¹⁷⁴ in helix 4; Val²⁰⁶, Ala²¹⁰, Val²¹³-Phe²¹⁴ in helix 5; Trp²⁸⁴, Phe²⁸⁷-Phe²⁸⁸, Gln²⁹¹ in helix 6; and Phe³⁰⁷, Leu³¹⁰, Ala³¹⁴ and Asn³¹⁷ in helix 7 appeared to be the most important ones. Many of these residues are invariant for either the GPCR superfamily or the neurophyseal (vasopressin V2R, V1aR and V1bR and oxytocin OR) subfamily of receptors. Moreover, some of the equivalent residues in V1aR have already been found critical for the ligand affinity [Mouillac et al., J. Biol. Chem, 270 (1995) 25771].     

Highly selective synthesis of 1-(silyl)-1-(boryl)ethenes via a ruthenium-catalyzed silylative coupling reaction

An efficient silylative coupling of trisubstituted vinylsilanes with dialkoxy(vinyl)boranes is described. Under optimum conditions the reaction offers a selective route to 1-(silyl)-1-(boryl)ethenes, which are potentially attractive intermediates in organic synthesis     

Olefin cross-metathesis with vinyl halides

The first successful example of olefin cross-metathesis with chloroalkenes is reported.     

Conformation‐Family Monte Carlo (CFMC): An Efficient Computational Method for Identifying the Low‐Energy States of a Macromolecule

A highly efficient method, Conformation‐Family Monte Carlo (CFMC), has been developed for searching the conformational space of a macromolecule and identifying its low‐energy conformations. This method maintains a database of low‐energy conformations that are clustered into families. The conformations in this database are improved iteratively by a Metropolis‐type Monte Carlo procedure, together with energy minimization, in which the search is biased towards investigating the regions of the lowest‐energy families. The CFMC method has the advantages of our earlier potential‐smoothing methods (in that it `coarse‐grains' the conformational space and exploits information about nearby low‐energy states), but avoids their disadvantages (such as the displacement of the global minimum at large smoothings). The CFMC method is applied to a test protein, domain B of Staphylococcal protein A. Independent CFMC runs yielded the same low‐energy families of conformations from random starts, indicating that the thermodynamically relevant conformational space of this protein has been explored thoroughly. The CFMC method is highly efficient, performing as well as or better than competing methods, such as Monte Carlo with minimization, conformational‐space annealing, and the self‐consistent basin‐to‐deformed‐basin method.     

Efficient Adsorption of Chromium Ions from Aqueous Solutions by Plant-Derived Silica

Nowadays, there is great interest in the use of plant waste to obtain materials for environmental protection. In this study, silica powders were prepared with a simple and low-cost procedure from biomass materials such as horsetail and common reed, as well as wheat and rye straws. The starting biomass materials were leached in a boiling HCl solution. After washing and drying, the samples were incinerated at 700 °C for 1 h in air. The organic components of the samples were burned leaving final white powders. These powders were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and low-temperature nitrogen sorption. The amorphous powders (biosilica) contained mainly SiO₂, as indicated by FTIR analysis. Horsetail-derived silica was chosen for testing the removal of dichromate ions from water solutions. This biosilica had a good ability to adsorb Cr(VI) ions, which increased after modification of the powder with the dodecylamine surfactant. It can be concluded that the applied procedure allowed obtaining high purity biosilica from plant waste with good efficiency. The produced biosilica was helpful in removing chromium ions and showed low cytotoxicity to human endothelial cells, suggesting that it can be safely used in environmental remediation.     

Acknowledgement to referees

Acknowledgements

Acknowledgement to referees