Bromination of 3-acyl-2-aminoindoles

Unlike 3-acylindoles, 3-acyl-2-aminoindoles display high selectivity on being electrophilically attacked in the benzene ring, and are substituted at the 6-position. At the same time, an unco-subsitution of the acyl group takes place (to the greatest extent — the formyl group). Direct bromination of 3-acyl- and 3-cyano-2-aminoindoles provides the 6-bromo- and 6,4-dibromo-2-aminoindoles and their derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 486–490, April, 1990.     

Formation of oligonucleotide-PNA-chimeras by template-directed ligation

DNA sequences have previously been reported to act as templates for the synthesis of PNA, and vice versa. A continuous evolutionary transition from an informational replicating system based on one polymer to a system based on the other would be facilitated if it were possible to form chimeras, that is molecules that contain monomers of both types. Here we show that ligation to form chimeras proceeds efficiently both on PNA and on DNA templates. The efficiency of ligation is primarily determined by the number of backbone bonds at the ligation site and the relative orientation of template and substrate strands. The most efficient reactions result in the formation of chimeras with ligation junctions resembling the structures of the backbones of PNA and DNA and with antiparallel alignment of both components of the chimera with the template, that is, ligations involving formation of 3'-phosphoramidate and 5'-ester bonds. However, double helices involving PNA are stable both with antiparallel and parallel orientation of the two strands. Ligation on PNA but not on DNA templates is, therefore, sometimes possible on templates with reversed orientation. The relevance of these findings to discussions of possible transitions between genetic systems is discussed.     

Head-column field-amplified sample stacking in presence of siphoning. Application to capillary electrophoresis-electrospray ionization mass spectrometry of opioids in urine

Capillary electrophoresis (CE) with head-column field-amplified sample stacking (FASS) in presence of a water plug inserted at the capillary tip is a robust approach providing a more than 1000-fold sensitivity enhancement when applied to low-conductivity samples that are analyzed in an integrated instrument. Employing modular systems comprising a small hydrodynamic buffer flow (siphoning) towards the capillary end and featuring UV absorption or electrospray ionization mass spectrometric (MS) detection, insertion of a water plug is demonstrated to deteriorate the performance of head-column FASS or making it unfunctional. Electroinjection in the absence of the water plug can be employed instead and is shown to provide a ng/ml sensitivity when applied to low conductivity samples. With some suction of sample into the capillary during electroinjection, contamination of the sample vial with buffer is thereby largely avoided. Electroinjection applied to the CE-ion trap MS-MS and MS-MS-MS analysis of twofold diluted urines, urinary solid-phase extracts and urinary liquid-liquid extracts is shown to provide much improved sensitivity compared to hydrodynamic injection of these samples. With electroinjection from diluted urine and urinary solid-phase extracts, the presence of free opioids and their glucuronic acid conjugates can be unambiguously confirmed in urines that were collected after single-dose administration of small amounts of opioids (tested with about 7 mg codeine and 25 mg dihydrocodeine, respectively). Thus, CE-multiple MS with direct electroinjection of opioids from untreated urines could prove to become a rapid and simple approach for unambiguous urinary testing of drug abuse. Procedures leading to the reduction of siphoning in modular CE setups are briefly discussed as well.     

Effect of the nature of the metal oxide on selective transformation of methane under unsteady conditions in the absence of oxidant in the gaseous phase

The catalytic transformation of methane into higher hydrocarbons was studied under unsteady conditions on oxides of various metals (Pb, Fe, Nb, Ti, Cd, Mo, Mg, Zn, Zr, Bi, Mn), and also on Sr-, La-, Y-, and Mn-containing oxides of perovskite structure. It is shown that the effectiveness of the catalysts not only depends on their chemical composition, but also is determined to a considerable degree by the specific surface of the oxides. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 252039 Kiev, Prosp. Nauki, 31, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 91–95, March–April, 1997.     

Acid-base properties of indolylglyoxal and some acetylindoles

A spectrophotometric study of the acid-base properties of 3-acylindoles showed that they were stronger acids than the alkylindoles. It was found that protonation of these compounds occurs at the carbonyl group. For indolylglyoxal, 3-acetylindole, and 1-methyl-3-acetylindole the pK_b was determined; the pK_afor indolylglyoxal and 3-acetylindole was measured in 50% aqueous methanol.Translated from Khimiya Geterotsiklicheskhikh Soedinenii, No. 12, pp. 1621–1624, December, 1987.     

X-ray studies of supported copper-aluminium catalysts

Structural peculiarities of the formation of copper-aluminium catalysts at copper concentrations <10 wt% and calcination temperatures of 573–1173 K have been studied.

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<10% . 573–1173°K.

     

Line widths of the 3800 Å singlet transitions in crystalline anthracene

The theory of resonance coupling of Frenkel excitons and phonons is extended to two molecules per unit cell. Intra- and inter-band scattering for the two Davydov components can thus be dealt with on the same footing. Restrictions to nearest neighbour interactions have been removed. Application to anthracene shows that the contribution of librational phonons to the scattering is approximately one hundred times larger than that of translational phonons. The widths of the anthracene components are shown to fit the calculated coupling and known phonon frequencies satisfactorily.     

Determination of aflatoxins in peanut products using reverse phase HPLC

A high performance liquid chromatographic (HPLC) method is described for the determination of the four major aflatoxins, B1, B2, G1 and G2, in peanut products. The aflatoxins are extracted by adapting a procedure developed by Pons (1) at the SRRC, USDA, and quantitated utilizing a new 5 mum reverse-phase column with NaCl/acetontrile/methanol mobile phase (3 + 1 + 1). The 5 mum column achieved baseline resolution of each of the four aflatoxins. Retention times and peak heights were reproducible. The procedure was successfully applied to several types of peanut products and was applicable to both roasted and unroasted peanuts, which is a decided advantage over the current CB and BF extraction methods. Additionally, it can be used for sweetened peanut matrixes with no interferences in the chromatography. The total time required for sample preparation and aflatoxin determination is less than 1.5 hours.     

Intramolecular metal—double bond interactions : VII. Intramolecular cyclization of alkenyl derivatives of lithium,aluminum, gallium and indium

The intramolecular cyclization reactions of tri-1-hex-5-enyl Group III derivatives and of 1-hex-5-enyllithium have been investigated and it is proposed that the reactions may be depicted as internal addition across the terminal double bonds of the alkenyl species. The cyclization reaction proceeds more readily for the 1-hex-5-enyl derivatives than for any other chain length and is dependent on temperature, concentration and solvent. ¹H NMR data and cryoscopic molecular weight data are presented for several diisobutyialkenyl- and diisobutylalkyl-aluminum derivatives. These data have been interpreted in terms of a direct intramolecular interaction between the metal center and the π-electron system of the olefinic site. The intramolecular cyclization reactions for the 1-hept-6-enyl, 1-oct-7-enyl- and 1-undec-10-enylaluminum derivatives also were investigated and it was found that cyclization occurred only for the 1-hept-6-enyl derivative.     

Alkyl–oxygen bond formation in the mass spectra of α-chloromethyl aryl sulphones

When subjected to electron-impact, chloromethyl aryl sulphones (II, X = Cl) fragment predominantly by the loss of CH₂Cl from the molecular ion followed by the loss of SO₂ and in most cases the appropriate metastable peaks are present to confirm the transitions. In addition, alkyl–oxygen bond formation in the molecular ion was revealed by the presence of prominent peaks corresponding to the [R? ?-SO]⁺ ions. In most spectra no evidence for aryl–oxygen bond formation could be found and thus the presence of the chlorine atom was able to effectively reverse the direction of skeletal rearrangement reported for aryl methyl sulphones.