A new synthesis of 1,5-dihydropyridazino[3,4-b]quinoxalines and 2-(pyrazol-4-yl)quinoxalines

The reaction of 6-chloro-2-(l-methylhydrazino)quinoxaline 1-oxide 3 with acetylenedicarboxylates gave the 8-chloro-1-memyl-1,5-dihydropyridazino[3,4-b]quinoxaline-3,4-dicarboxylates 4a,b and 2-(pyrazol-4-yl)quinoxaline 1-oxides 5a,b . The formation of compounds 4a,b would follow the 1,3-dipolar cycloaddition reaction, subsequent 1,2-hydrazino migration, and then dehydrative cyclization, while the production of compounds 5a,b would proceed via the addition of the hydrazino group to acetylene-dicarboxylate leading to the construction of a pyrazole ring, followed by rearrangement of the pyrazole ring. Compounds 5a,b were deoxidized with phosphoryl chloride/N,N-dimethylformamide to change into the 4-(quinoxalin-2-yl)pyrazole-3-carboxylates 8a,b .     

Intercalation of n-Alkylamines and n-Alkyldiamines into γ-Zirconium Phenylphosphonate Phosphate

Crystalline -zirconium phenylphosphonate phosphate was prepared according to Yamanaka's method and the intercalation behavior of n-alkylamines and n-alkyldiamines were investigated. In the case of n-alkylamines, a linear increase in interlayer distance was observed up to a carbon atom number of 12, whereas in n-alkyldiamines, only two di-amines, ethylenediamine and propylenediamine, were intercalated with respective increases in the interlayer distance. The increment of interlayer distance in both monoamines and diamines indicates the formation of a monomolecular layer in the interlayer region of the host, in contrast to the case in -zirconium phosphate as a host.     

Influence of a skull cranial window on the measurement of haemoglobin concentration in cortical tissue by multi-spectral imaging analysis

The simplified cranial window, which is transparent thinned skull, has been used for the optical imaging of cortical tissue of small animals to measure the concentration change in haemoglobin as an intrinsic signal of brain activation. The multi-spectral images of the cortical tissue of guinea pigs through the skull cranial window were compared with those of the exposed cortex to evaluate the influence of the scattering and absorption properties of the skull on the measurement of the concentration change in haemoglobin. Although skull thickness affects the sensitivity of the optical signal due to a decrease in mean optical path length in the cortical tissue, the influence of the skull cranial window on the wavelength dependence of optical path length can be ignored when the skull thickness is less than approximately 100 mm. Accurate concentration changes in oxygenated and deoxygenated haemoglobins can be calculated from the optical signal measured through a skull cranial window and the wavelength dependence of optical path length for the exposed cortex.     

Improvement of ozone yielding rate in atmospheric pressure barrierdischarges using a time-modulated power supply

The ozone (O₃) yielding rate of a high-pressure thin-gap barrier discharge was improved using a time-modulated power supply. The maximum improvement reached more than 20% compared with a continuous-wave power supply. The rate was strongly dependent on the discharge-off time, with the optimum one corresponding to the O₂ removal time from the discharge space. Dependence of the yielding rate on the off-time was numerically calculated using O and O₃ rate equations     

One-pot reactions of bicyclic zinc enolate generated from Ni-catalyzed reductive cyclization to furnish octahydro-4,7-ethanobenzofuran-9-one derivatives

The one-pot reactions of catalytically generated bicyclic zinc enolate with various electrophiles are reported. The zinc enolate as a key intermediate is efficiently delivered from Ni-catalyzed reductive cyclization of alkynyl cyclohexadienone. Employing aldehydes, imine, nitroalkene, and α,β-unsaturated carbonyl compounds as electrophiles, this new class of one-pot reactions gave multi-functionalized cis-hydrobenzofurans and octahydro-4,7-ethanobenzofuran-9-one derivatives in moderate to good yields.     

How many dimensions are required to approximate the potential energy landscape of a model protein?

A scheme to approximate the multidimensional potential energy landscape in terms of a minimal number of degrees of freedom is proposed using a linear transformation of the original atomic Cartesian coordinates. For one particular off-lattice model protein the inherent frustration can only be reproduced satisfactorily when a relatively large number of coordinates are employed. However, when this frustration is removed in a Go-type model, the number of coordinates required is significantly lower, especially around the global potential energy minimum. To aid our interpretation of the results we consider modified disconnectivity graphs where a measure of the structural diversity and a metric relation between the stationary points are incorporated.     

Protein solubilising and stabilising ionic liquids

We report a family of biocompatible ionic liquids (ILs) which are able to dissolve significant amounts of proteins such as cytochrome c and in which ATR-FTIR spectroscopy results show retention of secondary structure to extreme temperatures.     

Regioselectivity in benzotropolone formation between catechins and proanthocyanidins

A theaflavin-related benzotropolone pigment formed between procyanidin B-1 and (-)-epigallocatechin was synthesized enzymatically for the first time. The condensation occurred regioselectively at the extension (upper) unit of the procyanidin, probably due to a steric effect.     

Stereoselective ring expansion via bicyclooxonium ion. A novel approach to oxocanes

[reaction: see text] The stereoselective 1,4-rearrangement-ring expansion of tetrahydrofurans via bicyclo[3.3.0]oxonium ions was developed to synthesize oxocanes. On the basis of this rearrangement, the stereoselective synthesis of 2,8-syn-2,8-dimethyloxocane was accomplished.