Direct synthesis of pyran-lactones related to naphthoquinoneantibiotics

Simple benzopyrans with a fused γ-lactone unit are prepared from an o-disubstituted arene by direct intramolecular alkoxycarbonylation/lactonization promoted by palladium diacetate; the process gives high yields and moderate stereoselectivity, favoring the $\text{cis}$ lactone over $\text{trans}$ by a factor of 5:1.     

Upper limit for DD production in pp interactions at C.M. energy of 55 GeV

From a search for e^±μ^± production at the CERN ISR an upper limit of 0.92 μb (95% confidence limit) has been inferred for σ·B_e·B_μ for the reaction $\text{p}\text{+}\text{p}\text{→}\text{D}\text{+}\text{D}\text{+}\text{X}\text{at}\text{√s}\text{of}\text{55}\text{GeV}$.     

The impact of ice particle roughness on the scattering phase matrix

The goal of this study is to explore the influence of ice particle habit (or shape) and surface roughness on the scattering phase matrix. As an example, reported here are the results for two wavelengths: 0.67 and 1.61 μm. For this effort, a database of single-scattering properties has been computed for a set of habits including hexagonal plates, hollow and solid columns, hollow and solid 3D bullet rosettes, droxtals, aggregates of solid columns, and aggregates of plates. The database provides properties for each of the habits at 101 wavelengths between 0.45 and 2.24 μm for smooth, moderately roughened, and severely roughened particles. At each wavelength, the scattering properties are provided at 233 discrete particle diameters ranging from 2 to 10,000 μm. A single particle size distribution from a very cold ice cloud sampled during the CRYSTAL-FACE field campaign (T_cld=–76 °C) is used to illustrate the influence of habit and roughness on the phase matrix. In all, four different habit mixtures are evaluated. The nonzero elements of the phase matrix are shown to be quite sensitive to the assumed habit, particularly in the case of ?P₁₂/P₁₁ that is associated with the degree of linear polarization of scattered radiation. Surface roughness is shown to smooth out maxima in the scattering phase function and in the other elements of the phase matrix, consistent with other studies. To compare with the theoretical simulations of the phase matrix for smooth and roughened particles, a full year of cloud-aerosol lidar with orthogonal polarization (CALIOP) data from 2008 is analyzed to provide global statistics on the values of P₁₁ and P₂₂/P₁₁ in the backscattering direction. In a comparison of two of the habit mixtures (one used for MODIS Collection 5 and another that incorporates new habits including hollow bullet rosettes and aggregates of plates) with the CALIOP data, the values for P₁₁ are higher regardless of the degree of particle surface roughness, and the values for P₂₂/P₁₁ are lower than those for CALIOP. Further investigation is warranted to better understand this discrepancy.     

A BMAP|G|1-analysis based on convolution calculus

Stochastic models of high-speed communication systems typically require the analysis of special Markov additive processes, known thus far as “batch Markovian arrival processes” (BMAPs). In most cases, the solution of nonlinear matrix equations of the form or is necessary, leading, in general, to severe numerical problems. Several efficient algorithms for that purpose have been reported in the literature. In this contribution, we present a new approach (the BMAP|G| 1-analysis), which is based on a convolution calculus for matrix sequences. The main results are the unified representation of Poisson, compound Poisson, and batch Markovian arrival processes by so-called convolutional exponential distributions, and the computation of the fundamental-period matrix G via so-called semi-convolutions. The resulting algorithms, in general, cannot outperform known algorithms as, for instance, those exploiting Horner schemes as proposed by D. M. Lucantoni and other authors, or the highly efficient cyclic reduction algorithm of D. Bini and B. Meini; nevertheless, they allow the direct computation of step matrices such as the “arrival matrices” A_n with and the component matrices G_n summing to G. Further, there is some hope that the proposed framework may lead to a unification of the theory in the sense that queues with arrival and/or service processes that are characterized by convolutional exponential distributions may possess formally similar properties, as known from the scalar case. Proceedings of the Seminar on Stability Problems for Stochastic Models. Hajdúszoboszló. Hungary, 1997. Part II.     

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Synthesis and structure of novel sugar-substituted bipyridine complexes of rhenium and 99m-technetium

Novel ligands have been obtained from the reaction of 4,4'-dibromomethyl-2,2'-bipyridine with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosylthiol, 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosylthiol or 2,3,4,6-tetra-O-acetyl-alpha-D-thioacetylmannopyranoside in which the sugar residues are thioglycosidically linked to the bipyridine in the 4,4'-position. Cleavage of the acetyl groups affords hydrophilic symmetric ligands with free hydroxyl groups. Reaction of the new glycoconjugated ligands (L) with [Re(CO)(5)Cl] yields fluorescent complexes of general formula [Re(L)(CO)(3)Cl], which were characterised by mass spectrometry, elemental analysis and (1)H and (13)C NMR, IR, UV/Vis and fluorescence spectroscopy. These complexes exhibit excellent solubility and stability in organic solvents or water, depending on the residues of the sugar. One complex, namely tricarbonyl-4,4'-bis[(2,3,4,6-tetra-O-acetyl-beta-D-glycopyranosyl)thiomethyl]-2,2'-bipyridinerheniumtricarbonylo chloride, has been characterised by X-ray crystallography. A non-symmetric structure of the complexes could be assigned. Radiolabelling of the unprotected ligands with [(99m)Tc(H(2)O)(3)(CO)(3)](+) affords the corresponding water-soluble technetium complexes (in quantitative yields), which were characterised by their HPLC radiation traces. The formed complexes are stable for several hours in the presence of histidine but show partial ligand-exchange after one day.     

Stereoselective synthesis of a MCHr1 antagonist

Melanin-concentrating hormone (MCH) is implicated in the feeding behavior in mammals affording a potential target to control overeating in people. Compound 1 (AMG 076) has been identified as a potent MCHr1 antagonist for the treatment of obesity. A synthesis suitable for the large-scale preparation of this lead candidate was developed to support preclinical studies. A Robinson annulation of benzylpiperidone and resolution of the desired enone from a mixture of the diastereomers afforded key intermediate 6 after a stereoselective hydrogenation. Subsequent Fischer indole synthesis with hydrazine 5 then provided the advanced intermediate, indole 2. Two complementary reductive amination strategies employing either aldehyde 3 or lactol 4 led to the synthesis of title compound 1.