Functionalized azabicycloalkane amino acids by nitrone 1,3-dipolar intramolecular cycloaddition

[reaction: see text] An efficient and operationally simple method for the synthesis of functionalized azaoxobicyclo[X.3.0]alkane amino acids has been devised. The key step is an intramolecular nitrone cycloaddition on 5-allyl- or 5-homoallylproline that was found to be completely regio- and stereoselective.     

Weak solution of the merged mathematical equations of the polluted atmosphere

Considered as a geophysical fluid, the polluted atmosphere shares the shallow domain characteristics with other natural large-scale fluids such as seas and oceans. This means that its domain is excessively greater horizontally than in the vertical dimension, leading to the classic hydrostatic approximation of the Navier–Stokes equations. In the past there has been proved a convergence theorem for this model with respect to the ocean, without considering pollution effects. The novelty of this present work is to provide a generalization of their result translated to the atmosphere, extending the fluid velocity equations with an additional convection–diffusion equation representing pollutants in the atmosphere.     

Local Behavior of <Emphasis Type="Italic">p</Emphasis>-harmonic Green’s Functions in Metric Spaces

We describe the behavior of p-harmonic Green’s functions near a singularity in metric measure spaces equipped with a doubling measure and supporting a Poincaré inequality.     

Electrocortical effects of MDMA are potentiated by acoustic stimulation in rats

Background  

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is known for its toxicological, psychopathological and abuse potential. Some environmental conditions, e.g. acoustic stimulation typical of the "rave scene" can influence the toxicity of this drug.     

Energy balance in dense microemulsions

A water-in-oil microemulsion composed of water, AOT and decane with volume fraction φ=0.50 and molar ratio X=40.8 was analysed by DSC. The percolation and the bicontinuous transitions as well as the melting endotherms and the freezing exotherms were measured. The main attention was focussed on the system energy balance. It was found that, by freezing the samples after the occurrence of the percolative transition, the total heat released is significantly less than the heat absorbed in the melting endotherms. A simple geometrical model was used as an analysis tool of the aforementioned energy difference. Since the system studied exhibits a percolative transition of dynamic type, on approaching the percolation threshold temperature (T≤T _p) and a static percolation for T≥T _p, the structural change from the connecting water-droplet-cluster to a connecting water channel was schematised in the model as a change from a sphere-necklace to a water-cylindrical channel of equal volume and equal length. The surface energy associated with the formation of the two different geometrical surfaces was evaluated and the amount of saved energy compared with the experimentally measured one.     

Semisynthesis of new D-seco-C-nor-taxane derivatives containing a polyfunctionalized furanosyl or cyclopentenyl or cyclopentyl C-ring

The synthesis of new D-seco-C-nor-taxane derivatives in which the D-ring has been deleted and the C-ring has been transformed into a new pentatomic ring, i.e., the polyfunctionalized tetrahydrofuranosyl and cyclopentenyl or cyclopentyl ring, was performed starting from baccatin III derivatives. The synthetic strategy adopted took advantage of the oxetane ring opening and disconnection of the C4-C5 bond, followed by an intramolecular condensation. The formation of furanosyl or cyclopentyl rings is strictly dependent on the presence of unprotected or protected oxygen at C-7 in the starting material. The reactions proceeded with good diastereoselectivity with control of the stereochemistry of one or two stereocenters.     

Increasing Complexity in Adamantyl Thioethers Characterized by Rotational Spectroscopy

We report on the synthesis and characterization using high-resolution rotational spectroscopy of three bulky thioethers that feature an adamantyl group connected to a sulfur atom. Detailed experimental and theoretical structures are provided and compared with the 1,1′-diadamantyl ether. In addition, we expand on previous findings concerning microsolvation of adamantyl derivatives by investigating the cluster formation between these thioethers and a water molecule. The investigation of such clusters provides valuable insights into the sulfur-centered hydrogen bonding in thioethers with increasing size and steric repulsion.     

Highly accurate determinations of CO(2) line strengths using intensity-stabilized diode laser absorption spectrometry

An intensity-stabilized laser absorption spectrometer, which incorporates a mirror-extended cavity diode laser, a temperature-stabilized gas cell, and a Michelson interferometer, was developed and applied to a highly accurate investigation of line intensity factors within the nu(1)+2nu(2) (0)+nu(3) combination band of carbon dioxide, around 2 microm wavelength, at a temperature of 296.0 K. This relatively complex apparatus enables one to observe the absorption line shape with high precision and accuracy in such a way that it is possible to retrieve the integrated absorbance with a relative uncertainty better than 0.1%. The absorption spectra were interpolated with the uncorrelated strong-collision model of Rautian and Sobel'man in order to take into account Dicke narrowing effects, thus obtaining an agreement at a level of a few parts per 10(-5). We report line strength values for the R(2)-R(18) transitions with an unprecedented level of accuracy, in the range between 0.1% and 0.15%. Finally, we discuss the possibility of providing a first experimental test of the theoretical model for molecular line strengths based on the Herman-Wallis expansion.     

Chemical composition and volatile constituents of Anthyllis barba-jovis

Six flavonol glycosides were isolated and identified from the aerial parts of Anthyllis barba-jovis L. (Leguminosae), together with two coumarins and D-pinitol, a taxonomic marker of Leguminosae family. The structural elucidation of all compounds was based on their (1)H- and (13)C-NMR spectral data and bidimensional experiments. The total flavonoid content was also determined, according to the method described in the Italian pharmacopoeia. In order to complete the phytochemical investigation on A. barba-jovis, the essential oils from flowers and seeds were obtained by hydrodistillation and analysed by GC-MS; fresh flowers were analysed also directly by solid phase micro extraction (SPME).