Enantioselective synthesis of nitroalkanes bearing all-carbon quaternary stereogenic centers through Cu-catalyzed asymmetric conjugate additions

The first examples of catalytic asymmetric conjugate addition (ACA) of alkylzinc reagents to trisubstituted nitroalkenes, leading to the formation of nitroalkanes bearing a quaternary carbon stereogenic center, are reported. Reactions are promoted in the presence of 4 mol % of a readily available amino acid-based phosphine and 2 mol % (CuOTf).C6H6. Cu-catalyzed reactions proceed efficiently in up to 98% ee and can be carried out with a variety of dialkylzinc reagents and trisubstituted nitroolefins. We highlight the synthetic utility of the products obtained by efficient conversion of optically enriched nitroalkanes to the corresponding carboxylic acids.     

高效液相色谱直接分离μ-FcCCHCoW(CO)5(CpCOOC2H5)簇合物对映体

将三（苯基氨基甲酸）支链淀粉酯涂敷在硅胶上制成了手性固定相．将支链淀粉与过量的苯异氰酸酯在吡啶中反应得到的苯基氨基甲酸酯溶解并涂敷在用３－氨基丙基三乙氧基硅烷处理过的硅胶上，涂敷量为０．４５／２．５５（重量比）．用此手性固定相拆分了外消旋的簇合物μ－ＦｃＣＣＨＣｏＷ（ＣＯ）５（ＣｐＣＯＯＣ２Ｈ５）．拆分在室温下进行，洗脱液为甲醇，流速为０．５ｍＬ／ｍｉｎ．     

New syntheses and chemistry of hexafluorotropone

Two new routes to hexafluorotropone have been developed, one from hexachlorotropone and a superior synthesis from hexafluorobenzene. Hexafluorotropone was found to be a very weak base, with a conjugate acid pK(a) of -6.2 +/- 0.5. The tropone adds in [6 + 4] fashion to cyclopentadiene and photocyclizes to hexafluorobicyclo[3.2.0]hepta-3,6-dien-2-one. Lithium hydroxide in benzene transforms the tropone into pentafluorotropolone, which functions as a bidentate ligand.     

T(h)-symmetrical hexakisadducts of C(60) with a densely packed pi-donor shell can act as energy- or electron-transducing systems

For the first time several T(h)-symmetrical hexakisadducts of C(60) bearing up to six electro- and photoactive o-phenylene diamine or 9,10-dialkoxyanthracene moieties were synthesized and subjected to photoinduced electron/energy-transfer studies. Both donors form a densely packed pi-donor shell surrounding the fullerene core. In these novel core-shell ensembles (7 and 19), either an efficient energy transfer from the dialkoxyanthracene periphery, or an electron transfer from the o-phenylene diamine periphery transduces the flow of excited-state energy or electrons, respectively, to the fullerene moiety, which resides in the central core. Due to the relatively high reduction potential of the fullerene core, which is anodically shifted by approximately equal to 0.7 V, compared with that of pristine C(60), the outcome of these intramolecular reactions depends mainly on the donor ability of the peripheral system. Interestingly, the charge-separated state in the o-phenylene diamine heptad (7; tau=2380 ns in benzonitrile) is stabilized by a factor of 20 relative to the corresponding o-phenylene diamine dyad (6; tau=120 ns in benzonitrile), an effect that points unequivocally to the optimized storage of charges in this highly functionalized fullerene ensemble.     

Uniform thin films of poly-3,4-ethylenedioxythiophene (PEDOT) prepared by in-situ deposition

In-situ deposited thin films of the conducting polymer poly-3,4-ethylenedioxythiophene (PEDOT) have been prepared on hydrophilic and hydrophobic substrates and characterized by UV-Vis spectroscopy, atomic force microscopy and resistivity measurements.     

Self-organization of a sulfonamido-porphyrin in Langmuir monolayers and Langmuir-Blodgett films

Langmuir monolayers (LM) and Langmuir-Blodgett (LB) films of pure lipophilic meso-tetra(4-dodecylaminosulfophenyl)porphyrin (PC12) and mixed with the anionic surfactant sodium hexadecylsulfate (SHS) were studied. The molecular packing and structure of PC12 and PC12-4SHS with variable surface pressure were investigated by surface pressure-area measurements, steady-state absorption, fluorescence emission and anisotropy, as well as by fluorescence lifetime imaging microscopy (FLIM). At low surface pressure, the porphyrin molecules are organized with the rings tilted on the water surface whereas at high surface pressure the porphyrin rings achieve a more perpendicular arrangement. Using the FLIM images a gradual change of aggregates into large "islands" is observed. Different patterns are observed in the pure PC12 multilayer films (n = 3 and 5) with ordered patches superimposed which are not observed in the PC12-4SHS multilayer LB films.     

Mass spectrometric characterization of two novel inflammatory peptides from the venom of the social wasp Polybia paulista

The social wasp P. paulista is relatively common in southeast Brazil causing many medically important stinging incidents. The seriousness of these incidents is dependent on the amount of venom inoculated by the wasps into the victims, and the characteristic envenomation symptoms are strongly dependent on the types of peptides present in the venom. In order to identify some of these naturally occurring peptides available in very low amounts, an analytical protocol was developed that uses a combination of reversed-phase and normal-phase high-performance liquid chromatography (HPLC) of wasp venom for peptide purification, with matrix-assisted laser desorption/ionization time-of-flight post-source decay mass spectrometry (MALDI-Tof-PSD-MS) and low-energy collision-induced dissociation (CID) in a quadrupole time-of-flight tandem mass spectrometry (QTof-MS/MS) instrument for peptide sequencing at the sub-picomole level. The distinction between Leu and Ile was achieved both by observing d-type fragment ions obtained under CID conditions and by comparison of retention times of the natural peptides and their synthetic counterparts (with different combinations of I and/or L at N- and C-terminal positions). To distinguish the isobaric residues K and Q, acetylation of peptides was followed by Q-Tof-MS analysis. The primary sequences obtained were INWLKLGKMVIDAL-NH(2) (MW 1611.98 Da) and IDWLKLGKMVMDVL-NH(2) (MW 1658.98 Da). Micro-scale bioassay protocols characterized both peptides as presenting potent hemolytic action, mast cell degranulation, and chemotaxis of polymorphonucleated leukocyte (PMNL) cells. The primary sequences and the bioassay results suggest that these toxins constitute members of a new sub-class of mastoparan toxins, directly involved in the occurrence of inflammatory processes after wasp stinging.     

Pulsed electrochemical detection of penicillins using three and four step waveforms

Aided by the construction of a custom potentiostat, a series of different PAD waveforms were compared to find the optimum detector for penicillin oxidation. The waveforms included standard 3-step direct and indirect PAD in addition to reverse-PAD and 4-step PAD. Two new waveforms, the indirect reverse-PAD and the 4-step indirect PAD were examined in the study. Under the solvent conditions of the study (0.01M acetate buffer, pH 4.6) the indirect waveforms yielded the best detectability for penicillin G while the reverse-PAD waveforms yielded the worst performance. The 4-step PAD methods did not improve detectability when compared to the 3-step types, but they did provide output peak profiles with better shapes and less tailing. Although indirect waveforms gave better detectability than direct detection in the 0.01M acetate buffer solution, the limits of detection for each were found to be differing functions of ionic strength. At higher acetate concentrations, direct PAD was more favorable than indirect detection.     

A theoretical study of the [4 + 4] dimerization of thioformylketene

[reaction and structure: see text] A theoretical study (B3LYP and G3MP2B3) of the dimerization of thioformylketene (1) was performed. Four pathways-two [4 + 2] pathways with thioformylketene (1), one [4 + 4] pathway with 1, and one [4 + 2] pathway involving 1 and thietone (11)-were considered. Interestingly, the [4 + 4] pathway with 1 had the lowest barrier (3.8 kcal/mol). The geometry of the transition state TS14 is unusual, with the forming bonds in the plane of the ketene. This suggests that the reaction is pseudopericyclic.