5-Arylidene Derivatives of Meldrum’s Acid as Synthons in Pyrano[4,3-b]pyran Synthesis

The reactions of 5-arylidene derivatives of Meldrum’s acid with ethyl vinyl ether or N-vinyl-2-oxazolidinone yielded trans-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, cis-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, or diastereoisomeric mixtures of pyrano[4,3-b]pyrans and reactions with 3,4-dihydro-2H-pyran afforded Michael adducts. The reactions of 5-arylidene derivatives of Meldrum’s acid with cyanoacetic acid derivatives do not provide appropriate pyrans.     

Electronic concentration of negatively-charged molecules on a microfabricated biochip

Various conditions leading to successful electronic concentration of negatively-charged molecules, notably oligonucleotides, on a microfabricated biochip have been studied. Tests on two chip designs have been performed. In the first generation biochip, which consisted of 12 electrodes 5 mm apart, fluorescent molecules were attracted to a positively-biased electrode leading to electronic concentration. In the second generation biochip, which consisted of eight electrodes 250 μm apart, much faster concentration rates were observed due to reduction in electrode spacing. These results are significant to design a pathogen detection biochip based on DNA hybridization assisted by electronic concentration.     

Multiply Borylated Arenes: X‐ray Crystal Structure Analyses and Quantum Chemical Calculations

Optimised synthesis procedures and results of X‐ray single crystal structure analyses for 4‐(dibromoboryl)toluene, 1, 3‐bis(dibromoboryl)benzene, 1, 4‐bis(dibromoboryl)benzene, and 1, 3, 5‐tris(dibromoboryl)benzene are reported. These compounds have also been studied by Hartree‐Fock (HF), density functional theory (DFT), and Mßller‐Plesset second‐order perturbation (MP2) methods in combination with the polarized double‐ζ valence (SVP) and polarized triple‐ζ valence (TZVP) basis sets of Ahlrichs and coworkers. A comparison of the quantum chemical results for optimised geometries and computed NMR chemical shifts with experiment is presented to test the quality of the various methods for this class of compounds. All DFT methods tested yield optimised geometries within the experimental error bars of 3σ for bond lengths, whereas larger deviations among the methods are observed for computed NMR chemical shifts. This calibration recommends the B3LYP/SVP combination as a reliable and computationally efficient level of theory to assess the structures and absolute and relative ¹H‐, ¹³C‐ and ¹¹B NMR shift values of borylated aromatic compounds in future investigations.     

Preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran)

A cycloaliphatic diepoxide is polymerised in the presence of poly(tetrahydrofuran) with hydroxy end-groups (PTHF). The cationic polymerisation is induced with an iodonium salt as initiator. The shear modulus as well as the glass transition temperature decreases with increasing amount of PTHF. Samples with 25 mol% PTHF of a M_n between 650 and 2900 show a rubber-like behaviour at room temperature. The maximum strain increases and the modulus of elasticity decreases with increasing M_n of the PTHF. During the polymerisation the samples shrink and the shrinkage increases with increasing M_n of the PTHF. The shrinkage is caused by the decomposition of the PTHF. After a long term thermal treatment the PTHF of the samples prepared with PTHF of high M_n had--in contrast to the samples prepared with PTHF of low M_n--nearly completely escaped out of the samples. This indicates that the ether bonds between the cyclohexane ring of the epoxy resin and the PTHF are much more stable than the ether bonds within the PTHF chains.     

High-performance column liquid chromatographic method for the simultaneous determination of buclizine, tryptophan, pyridoxine, and cyanocobalamin in tablets and oral suspension

An HPLC method was developed and validated for the simultaneous determination of buclizine, tryptophan, pyridoxine, and cyanocobalamin in pharmaceutical formulations. The chromatographic separation was carried out on an RP-C18 column using a mobile phase gradient of methanol, 0.015 M phosphate buffer (pH 3.0), and 0.03 M phosphoric acid at a flow rate of 1.0 mL/min and UV detection at 230, 280, and 360 nm, respectively, for buclizine, tryptophan, pyridoxine, and cyanocobalamin. The method validation yielded good results with respect to linearity (r>0.999), specificity, precision, accuracy, and robustness. The RSD values for intraday and interday precision were below 1.82 and 0.63%, respectively, and recoveries ranged from 98.11 to 101.95%. The method was successfully applied for the QC analysis of buclizine, tryptophan, pyridoxine, and cyanocobalamin in tablets and oral suspension.     

Binary HPLC-diode array detector and HPLC-evaporative light-scattering detector fingerprints of methanol extracts from the selected sage (Salvia) species

This study is focused on an important family of the sage (Salvia) species, with Salvia officinalis L. having a long-established position in European traditional medicine. Binary fingerprints (chromatographic profiles) of six different sage species were compared using HPLC coupled with two different detectors: the diode-array detector and the evaporative light-scattering detector. Advantages of using binary fingerprinting over single-detector fingerprinting are demonstrated and discussed, with selected examples. Experimental data are provided for a comparison of the chemical composition of sage samples originating from two harvesting seasons (2007 and 2008). A number of phytochemical standards (i.e., certain phenolic acids, flavonoids, and coumarin) were used that allowed identification and semiquantitative estimation of these particular compounds in the analyzed methanol extracts.     

Rational design of an aryl-C-glycoside catalyst from a natural product O-glycosyltransferase

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Highlights? 106 rationally designed chimeras were expressed in vivo and screened by HPLC-MS analysis ? One 12-amino acid protein segment is crucial for O- or C-glycosylation ? The sugar-acceptor postioning determines O- or C-glycosidic bond formation ? Ala substitutions revealed the key spots for glycosylation