Substituent effects on the tautomer ratios between the hydrazone imine and diazenyl enamine forms in side-chained quinoxalines

The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 9–11 were synthesized by the reaction of the quinoxalines 6–8 with various p-substituted benzenediazonium salts. Compounds 9–11 showed the tautomeric equilibria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The substituent effect on the tautomer ratios of A to B was studied by the nmr spectroscopy to clarify that the presence of the ester group R² on the hydrazone carbon and electron-donating p-substituent R¹ on the side chain benzene ring exhibited a tendency to increase the ratios of the tautomer A .     

Transition metal-catalyzed olefin arylation via C–H bond activation of arenes

In this article, two kinds of our transition metal-catalyzed olefin arylations are summarized and discussed. The first one is Ir-catalyzed novel anti-Markovnikov hydroarylation of olefins with benzene. Using this reaction catalyzed by [Ir(μ-acac-O,O′,C₃)(acac-O,O′)(acac-C₃)]₂ (acac = acetylacetonato), 1, straight-chain alkylarenes, which were not obtainable by the conventional Friedel-Crafts aromatic alkylation with olefins, were able to be successfully synthesized directly from arenes and olefins with the higher selectivity than that of branched alkylarenes. This is the first efficient catalyst which shows the desirable high regioselectivity. The reaction of benzene with propylene gave n-propylbenzene and cumene in 61% and 39% selectivities, respectively, and the reaction of benzene and styrene afforded 1,2-diphenylethane in 98% selectivity. The reaction of alkylarene and olefin showed meta and para orientations. A wide range of olefins and arenes can be employed for the synthesis of alkylarenes. The mechanism of the reaction involves C–H bond activation of benzene by Ir center to form Ir–phenyl species. The second reaction is Rh-catalyzed oxidative arylation of ethylene with benzene to directly produce styrene, namely one-step synthesis of styrene. The reaction of benzene with ethylene catalyzed by Rh(ppy)₂(OAc) (ppyH = 2-phenylpyridine, OAc = acetate), 3 with Cu oxidizing agent gave styrene and vinyl acetate in 77% and 23% selectivities, respectively, in contrast to those by Pd(OAc)₂, 47% of styrene and 53% of vinyl acetate. The mechanism of the reaction involves Rh-mediated C–H bond activation of benzene, which appears to be a rate-determining step. Furthermore, Rh complexes in a Rh(I) oxidation state at the beginning of the reaction work as catalysts for the reaction by addition of acacH and O₂ without any oxidizing agent, like Cu salt.     

Novel ring transformation reactions of xanthine derivatives

The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed.     

Application of ion-exchange cartridge clean-up in food analysis IV. Confirmatory assay of benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin, in bovine tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the confirmation of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using electrospray ionization liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS) with a product ion scan mode. All penicillins gave [M-H]-, [M-H-CO2]- and [M-H-141]- as the product ion, when [M-H]- was selected as the precursor ion. Combination of an ion-exchange cartridge clean-up and the LC-ESI-MS-MS method can reliably identify all of these penicillins fortified at a concentration of 0.05 mg/kg in bovine tissues, including liver, kidney and muscle. The limits of confirmation satisfy the maximum residue limits for each of the penicillins established by the World Health Organization, US Food and Drug Administration, European Union and Japan.     

Circularly polarized luminescence (CPL) characteristics of hydrophobic pyrene derivatives/γ-cyclodextrin (γ-CD) complexes in aqueous solution dissolved by grinding

Circularly polarized luminescence (CPL) organic dyes are currently receiving a great interest, but there are still not many reported observations of CPL spectra of hydrophobic dyes from aqueous solution. We have prepared hydrophobic pyrene derivatives and dissolved them into aqueous solutions with γ-cyclodextrin (γ-CD) by using grinding technique. Among these derivatives, (pyrene-1-carbonyl)serine (PySer) forms a spatially restricted dimer in the hydrophobic chiral cavity of γ-CD and exhibits excimer emission with a high quantum yield of Φ_f?=?0.68. In addition, circular dichroism and CPL signals were induced for the complex. The strong g_CPL value of g_CPL?=?+?2.2?×?10^?3 was obtained, which may be attributed to the interaction between the hydroxyl groups in the side chain of PySer with those of γ-CD and it strengthens the chiral dimeric structure.

Graphic abstract

     

Studies of the polymerization of diallyl compounds. XXII. Polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures

The polymerization of diallyl oxalate was conducted in the presence of radical initiators at a high temperature range of 80–180°C; a large decrease in degree of polymerization, an increase in residual unsaturation of the resulting polymer, and the evolution of carbon dioxide were observed with the elevation of temperature. These findings were reasonably interpreted by considering the dismutation of the uncyclized growing radical to yield the allyl radical, carbon dioxide, and polymer carrying a terminal double bond. The kinetics of the polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures were also discussed in detail.     

Detection of potential membrane receptor proteins concerning circadian rhythmic leaf movement of legumes using novel photoaffinity probe compounds

Circadian rhythmic plant leaf movement, called nyctinasty, is controlled by a time-course change in the internal concentration of the leaf-movement factor in the plant body. We report that specific binding protein (210 and 180 kDa) for a leaf-movement factor, potassium lespedezate, is contained in the plasma membrane of the plant motor cell. These proteins would be potential receptors for leaf-movement factor to control the leaf movement.     

Binding of sulfonamides to erythrocyte proteins and possible drug-drug interaction

The mode of binding of sulfonamides to erythrocyte proteins and possible drug-drug interaction between those compounds in erythrocytes resulting in changes in tissue levels were studied in rats using zonisamide (a novel antiepileptic agent possessing a sulfonamide group), several other sulfonamides and some antiepileptics without a sulfonamide group. In Michaelis-Menten plottings, the sulfonamide was found to be concentrated into erythrocytes in vitro and in vivo in a saturable high-affinity mode and in a linear low-affinity mode at ordinary therapeutic plasma levels through a simple diffusion process. Concentration in erythrocytes was affected by the presence of albumin in the extracellular medium. The cellular sulfonamide was readily replaced by extracellular sulfonamides in vitro. Even in vivo, erythrocyte levels of zonisamide were lowered by administration of other sulfonamides, although the plasma and tissue levels were not significantly changed since the plasma and tissue compartments of zonisamide were large relative to the erythrocyte compartment at ordinary therapeutic dose levels of zonisamide in animals and man. Therefore, disposition of zonisamide was not significantly influenced by other sulfonamides, but it is suggested that drug-drug interaction affecting the tissue levels may occur for a combination of sulfonamides with extremely different affinities for erythrocytes and low therapeutic plasma levels.     

Effect of substituent on the enantioselectivity for lipase-catalyzed kinetic resolution of glycerol derivatives

The lipase-catalyzed transesterifications of various substituted diphenyl 1,2-ketals of glycerol have been investigated. Efficient modification of the substrate structure with bis(4-bromophenyl) ketal was found to enhance the enantioselectivity up to E=57 at 0 °C.