Direct conversion to 2-phenyl-4-quinolones via a 4-alkoxyflavylium salt from a naturally occurring flavanone

A flavanone, in which a hydroxyl group at the 5-position was protected with a methyl group, converted to the corresponding 5-methoxy-2-phenyl-4-quinolone via flavylium salt under mild conditions. Flavanone-O-rhamnoglucoside, naringin, was also converted to 5-methoxy-2-phenyl-4-quinolon-7-O-rhamnoglucoside in the same way in an overall 25% yield.     

Electrochemical reactors for NO decomposition. Basic aspects and a future

The electrochemical reduction of nitric oxide in the presence of the excess oxygen was reviewed. It was shown that the selectivity and activity of the cathodes is strongly dependent on the composition and on the microstructure of the cathode material. A concept of electrochemical reactor with multilayer electro-catalytic electrode was proposed and successfully designed in Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. The typical values of current efficiency in such electrochemical reactors are of the order of 10–20% at gas composition: 1,000 ppm NO and 2% O₂ balanced in He and at gas flow rate 50 ml/min. The value of current efficiency depends on the functional multi-layer electrode composition, structure, and operating temperature. Such electrochemical reactors show the value of NO/O₂ selectivity (ν _sel) higher than 5 (ν _sel > 5) at intermediate temperature and up to ν _sel = 25 at low temperature operation. It was shown that multilayer electro-catalytic electrode should consist at list from three main functional layers: cathode, electro-catalytic electrode, covering layer, in order to operate as an electrode with high selectivity.     

Cover Picture: Theoretical Study on the Halogen–Zinc Exchange Reaction by Using Organozincate Compounds (Chem. Eur. J. 23/2009)

Density functional theory and fragment‐energy analysis have been used to probe the mechanism of the halogen–zinc exchange reaction. In their Full Paper on page 5686 ff. , M. Uchiyama, S. Nakamura et al. discuss three important factors in this reaction: The effect of the halogen species, the effect of the alkyl ligand on zinc, and the effect of the substrate nature.

     

Application of the Perimeter Model to the Assignment of the Electronic Absorption Spectra of Gold(III) Hexaphyrins with [4n+2] and [4n] π‐Electron Systems

Expanded porphyrins : The electronic excited states of two forms of meso‐hexakis(pentafluorophenyl)‐substituted gold(III) hexaphyrin(1.1.1.1.1.1), such as that depicted, have been investigated by density functional calculations and magnetic circular dichroism spectroscopy to assign their low‐energy excited singlet states.

     

Ion-exclusion chromatography with the direct UV detection of non-absorbing inorganic cations using an anion-exchange conversion column in the iodide-form

An ion-exclusion chromatographic method for the direct UV detection of non-absorbing inorganic cations such as sodium (Na⁺), ammonium (NH₄⁺) and hydrazine (N₂H₅⁺) ions was developed by connecting an anion-exchange column in the I⁻-form after the separation column. For example, NH₄⁺ is converted to a UV-absorbing molecule, NH₄I, by the anion-exchange column in the I⁻-form after the ion-exclusion separation on anion-exchange column in the OH⁻-form with water eluent. As a result, the direct UV detection of Na⁺, NH₄⁺ and N₂H₅⁺ could be successfully obtained as well as the well-resolved separation. The calibration graphs of the analyte cations detected with UV at 230 nm were linear in the range of 0.001-5.0 mM. The detection limits at S/N = 3 of the cations were below 0.1 μM. This method was applied to real water analysis, the determination of NH₄⁺ in river and rain waters, or that of N₂H₅⁺ in boiler water, with the satisfactory results. This could be applied also to low- or non-absorbing anions such as fluoride or hydrogencarbonate ions by the combination of a weakly acidic cation-exchange resin in the H⁺-form as the separation column and the anion-exchange conversion column.     

A proteome-wide analysis of domain architectures of prokaryotic single-spanning transmembrane proteins

We performed a proteome-wide survey of the domain architectures in single-spanning transmembrane (TM) proteins (single-spannings) from 87 sequenced prokaryotic (Bacterial and Archaean) genomes by assigning Pfam domains to their N-tail and C-tail loops. Out of 14,625 single-spannings, 3,516 sequences have at least one domain assigned, and no domains were assigned to 7,850, with the remaining 3,259 with less reliable assignment. In the domain-assigned sequences, 3116 sequences are with at most two domains, and the other 400 sequences with more than two. The assigned domains distribute over 651 Pfam families, which account for 11.4% of the total Pfam-A families. Among the 651 families are mostly soluble-protein-originated ones, but only 21 families are unique to TM proteins. The occurrence frequency of the individual domain families follows a power-law, that is, 264 families occur only once, 106 just twice, and the families appeared more than 30 times are counted by only 39. It is found that the great majority of the sequences having one or two domains are of the type II topology with the C-tail loop containing domains on it. On the contrary, the N-tail loop of the same type topology seldom carries domains. Importantly, the assigned domains are always found on the tail loops longer than 60 residues, even for the small domains with less than 30 residues. There are still as many as 5,800 sequences without assigned domains in spite of having at least one long tail, on which no less than 1,000 novel domain families are expected most likely to lie concealed unknown yet. We also investigated the domain arrangement preference and the domain family combination patterns in 'singlets' (single-spannings with one assigned domain) and 'doublets' (with two domains).     

Photoinversion of cisoid/transoid binaphthyls

Axially chiral binaphthyl-azobenzene cyclic dyads in which the two moieties are connected by two linkers of different lengths were synthesized. In the case of benzylated-binaphthyl analogue 2b, photoirradiation resulted in a dramatic change of the CD spectrum and optical rotation. Experimental and theoretical analyses indicated that the dihedral angle of the two naphthalene rings is strongly coupled to the azobenzene photoisomerization; cis-azobenzene induces a transoid-binaphthyl structure, while trans-azobenzene induces a cisoid-binaphthyl structure.     

强碱阴离子交换树脂及碱性洗脱剂的离子排阻/阴离子交换色谱法同时测定NH4+ ，NO2-和NO3-（英文）

Ion-exclusion/anion-exchange chromatography(IEC/AEC) on a combination of a strongly basic anion-exchange resin in the OH——form with basic eluent has been developed.The separation mechanism is based on the ion-exclusion/penetration effect for cations and the anion-exchange effect for anions to anion-exchange resin phase.This system is useful for simultaneous separation and determination of ammonium ion(NH+4),nitrite ion(NO-2),and nitrate ion(NO-3) in water samples.The resolution of analyte ions can be manipulated by changing the concentration of base in eluent on a polystyrene-divinylbenzene based strongly basic anion-exchange resin column.In this study,several separation columns,which consisted of different particle sizes,different functional groups and different anion-exchange capacities,were compared.As the results,the separation column with the smaller anion-exchange capacity(TSKgel Super IC-Anion) showed well-resolved separation of cations and anions.In the optimization of the basic eluent,lithium hydroxide(LiOH) was used as the eluent and the optimal concentration was concluded to be 2 mmol/L,considering the resolution of analyte ions and the whole retention times.In the optimal conditions,the relative standard deviations of the peak areas and the retention times of NH+4,NO-2,and NO-3 ranged 1.28%-3.57% and 0.54%-1.55%,respectively.The limits of detection at signal-to-noise of 3 were 4.10 μmol/L for NH+4,1.87 μmol/L for NO-2 and 2.83 μmol/L for NO-3.