Optogalvanic spectra of calcium in the 6090–6760 Å region

Optogalvanic spectra of some 30 transitions of calcium originating from the ground state as well as from several excited states (4s4p ^1,3P, 4s3d ^1,3D, 4s5p ³P, 3d4p ³D, ³F) have been investigated using laser-irradiation of a low-current glow discharge in a thermionic diode. The influence of various experimental parameters such as bias field, oven temperature and buffer gas pressure on the spectra are reported. Seven previously unreported transitions are recorded including four forbidden transitions which violate the J selection rules. An interesting anomaly observed in the non-statistical population of the 4s3d ³D_3,2,1 multiplet is discussed where the populations of ³D₃:³D₂:³D₁ are in the ratio of 94:5:1. A possible explanation is based on avoided crossing between potential energy curves of the Ca-Ar molecule.     

A new route to trinuclear carbocyanines

Amides or vinylogous amides react with tosyl chloride-pyridine to form activated intermediates which condense with Fischer's base or their vinylogs to give carbocyanine structures. Under the same conditions formylated Fischer's base reacts with vinylogous Fischer's bases to give trinuclear carbocyanines in good yields. Their structure and the limitations of this route are discussed.     

Structural characterization of chondroitin/dermatan sulfate oligosaccharides from bovine aorta by capillary electrophoresis and electrospray ionization quadrupole time-of-flight tandem mass spectrometry

An analytical approach based on high-performance capillary electrophoresis (CE) in conjunction with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) has been developed for providing the basis to obtain new insights into the domain structure of the glycosaminoglycan (GAG) moiety of proteoglycans. The feasibility and performance of the off-line CE/ESI-QTOF-MS approach in GAG oligosaccharide analysis were assessed by screening a chondroitin/dermatan sulfate (DS) oligosaccharide mixture obtained from bovine aorta by enzymatic depolymerization by chondroitin B lyase. The CS/DS mixture was analyzed by CE using 50 mM ammonium acetate, pH 12.0, dissolved in aqueous methanol (2:3; v/v), as a CE carrier. Structural identification of the GAG components was achieved using off-line CE/nanoESI-QTOF-MS and-MS/MS experiments. ESI-QTOF instrumental parameters were found to play an important role in the MS screening of the CE-separated GAG species. By optimizing the ESI conditions, oligosaccharides differing in chain length and degree of sulfation could be detected. The building block composition, the size of the carbohydrate chain, as well as structural features of the repeating HexA-GalNAc, HexA-GalNAc(S) units, have been determined using MS/MS by applying collision-induced dissociation at low energies. Cleavage of GAG chains by chondroitin B lyase occurs with formation of structural markers useful for identification of IdoA-containing domains.     

Quantitative determination of usnic acid in Usnea lichen and its products by reversed-phase liquid chromatography with photodiode array detector

Usnic acid, a lichen substance, has a wide range of pharmaceutical applications, including antibiotic, antimycotic, antifeedant, antitubercular, antitumor, and analgesic activities. Some products containing usnic acid are marketed as weight control supplements; however, hepatotoxicity and acute liver failures were reported as severe side effects. The usnic acid content present in the plant materials and market products was analyzed by reversed-phase high-pressure liquid chromatography with a photodiode array detector at 233 nm. A Waters XTerra RP18 (150 x 4.6 mm; 5 microm particle size) column was the stationary phase; mobile phase was aqueous 0.1% acetic acid and acetonitrile gradient at flow rate of 1.0 mL/min. The temperature was held constant at 30 degrees C. The retention time of usnic acid was approximately 13.3 min. Acetone extraction of the samples took place with sonication. The precision of the method was confirmed by a standard deviation below 3.0% (n=3) and usnic acid recovery was 99.0%. Limit of detection was 0.4 microg/mL and the response was linear from 1.4 to 570.0 microg/mL with a correlation coefficient (R2) of 0.9991. The content of usnic acid in 4 raw materials and 22 finished products was analyzed.     

Fused pyrazolopyrimidines. I. Pyrazolo[4,3-e]-v-triazolo[1,5-a]pyrimidine. A new heterocyclic system

5-Azido-4-cyano-1-phenylpyrazole reacts with benzylcyanide in the presence of sodium methoxide to give the title ring system.     

Enantioselective catalytic epoxidation of nonfunctionalized prochiral olefins by dissymmetric chiral Schiff base complexes of Mn(III) and Ru(III) metal ions II

A series of new dissymmetric chiral Schiff base complexes has been obtained by a systematic condensation of (1S,2S)(+)-diaminocyclohexane and 3-acetyl-4-hydroxy-6-methyl-2-pyrone with salicylaldehyde, 5-chloro-, 5-methoxy-and 5-nitrosalicylaldehyde and by subsequent metallation with manganese and ruthenium. The characterization of the complexes 1–8 was accomplished by physico chemical studies viz. microanalysis, IR-, UV/VIS-, and CD spectral studies, optical rotation, molar conductance measurements and cyclic voltammetry. Enantioselective epoxidation of non functionalised olefins, viz. cis-stilbene, trans-3-nonene and trans-4-octene with iodosyl benzene as oxidant was demonstrated in the presence of catalytic amounts of chiral Mn(III) and Ru(III) dissymmetric Schiff base complexes. Good optical yields of epoxides were obtained for the catalyst 4 with the substrates trans-3-nonene and cis-stilbene.     

Thin-Layer Chromatographic Separation of Cadaverine and Ornithine,and Spectrophotometric Quantification

JPC – Journal of Planar Chromatography – Modern TLC -     

A 1H NMR study of 1,4-bis(N-hexadecyl-N, N-dimethylammonium)butane dibromide/sodium anthranilate system: spherical to rod-shaped transition

The effect of addition of sodium anthranilate to 5 mM micellar solutions of gemini surfactant 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide is investigated by ¹H NMR. The solubilization site of anthranilate anion near the micellar surface is inferred. In the micelles, the An⁻ ions intercalate among the surfactant headgroups producing morphological changes.     

O-silylated enolate phenylthialkylation: A synthesis of α,β-unsaturated 5- and 6-membered lactones.

ZnBr₂-catalysed phenylthioalkylation of ketene bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ- lactones.