Chiral Diphenylprolinol TES ether promoted conjugate addition-aldol-dehydration reactions between alpha,beta-unsaturated aldehydes and 2-N-protected amino benzaldehydes

A conjugate addition-aldol-dehydration reaction of alpha,beta-unsaturated aldehydes with 2-N-protected amino benzaldehydes has been developed. The process is promoted by (S)-diphenylprolinol TES ether to afford synthetically useful 1,2-dihydroquinolines in high enantioselectivities with good yields. [reaction: see text]     

Synthesis of propionamide pyridine and pyridine n‐oxide ligands

A new set of pyridine and pyridine N‐oxides functionalized with N,N‐dimethylpropionamide pendant groups in the 2‐ and 2,6‐positions have been prepared from the combination of 2‐chloromethylpyridine and 2,6‐bis(chloromethyl) pyridine with α‐lithio N,N‐dimethyl acetamide. The coordination interaction between 2‐(N,N‐dimethylpropionamide) pyridine N‐oxide ( 10 ) and Tb(NO₃)₃ has been unambiguously defined via single crystal X‐ray diffraction analysis of Tb( 10 )(NO₃)₃(H₂O).     

Synthesis of a 2,5-diaryloxazoline as a potential platelet-activating factor antagonist

2,5-Bis-(3,4,5-trimethoxyphenyl)-2-oxazoline ( 5 , MDL 100,270) was designed as a potential platelet-activating factor (PAF) antagonist on the basis of computer modeling comparison studies with known PAF antagonists. An efficient, four-step synthesis of oxazoline 5 was developed, starting from 3,4,5-trimethoxybenzaldehyde ( 6 ). Oxazoline 5 was found to inhibit the PAF-induced aggregation of human platelets with an IC₅₀ value of 708 μM.     

双核钌-DMBA双芳香炔化合物的合成和电化学性质

在弱碱性条件下,双核钌（Ⅲ）配合物Ru₂（DMBA）₄（NO₃）₂（DMBA=tetrakis-N,N''-dimethylbenzamidinate）与不同芳香炔反应（其中芳香基团包括：NAP^me,N-甲基-1,8-萘二甲酰亚胺;NAP^iso,N-异丙基-1,8-萘二甲酰亚胺;Naphth,萘;Ant,蒽）,制备了相应的端基炔取代配合物trans-Ru₂（DMBA）₄（C₂Ar）₂（Ar=NAP^me,1;NAP^iso,2;Naphth,3;Ant,4）。利用X射线晶体衍射测定了它们的结构。所有化合物的Ru-Ru 键长处于单键范围（0.245 0~0.249 1 nm）,它们均是抗磁性物质。进一步通过¹H NMR和UV-Vis-NIR光谱进行了表征。电化学研究表明,所有化合物显示出与芳香基团有关的2个可逆的单电子氧化还原过程（包括一个氧化过程和一个还原过程）。     

Addressing the Requirements of High‐Sensitivity Single‐Molecule Imaging of Low‐Copy‐Number Proteins in Bacteria

Single‐molecule fluorescence super‐resolution imaging and tracking provide nanometer‐scale information about subcellular protein positions and dynamics. These single‐molecule imaging experiments can be very powerful, but they are best suited to high‐copy number proteins where many measurements can be made sequentially in each cell. We describe artifacts associated with the challenge of imaging a protein expressed in only a few copies per cell. We image live Bacillus subtilis in a fluorescence microscope, and demonstrate that under standard single‐molecule imaging conditions, unlabeled B. subtilis cells display punctate red fluorescent spots indistinguishable from the few PAmCherry fluorescent protein single molecules under investigation. All Bacillus species investigated were strongly affected by this artifact, whereas we did not find a significant number of these background sources in two other species we investigated, Enterococcus faecalis and Escherichia coli. With single‐molecule resolution, we characterize the number, spatial distribution, and intensities of these impurity spots.     

Substituent effects on edge-to-face aromatic interactions

Chemical double mutant cycles have been used to measure the magnitude of edge-to-face aromatic interactions in hydrogen-bonded zipper complexes as a function of substituents on both aromatic rings. The interaction energies vary depending on the combination of substituents from +1.0 kJ mol-1 (repulsive), to -4.9 kJ mol-1 (attractive). The results correlate with the Hammett substituent constants which indicates that electrostatic interactions are responsible for the observed differences in interaction energy. The experiments can be rationalised based on local electrostatic interactions between the protons on the edge ring and the pi-electron density on the face ring as well as global electrostatic interactions between the overall dipoles on the two aromatic groups.     

Total Synthesis of Human Hepcidin through Regioselective Disulfide‐Bond Formation by using the Safety‐Catch Cysteine Protecting Group 4,4′‐Dimethylsulfinylbenzhydryl

A safety‐catch cysteine protecting group, S‐4,4′‐dimethylsulfinylbenzhydryl (Msbh), was designed and developed to expand the capabilities of synthetic strategies for the regioselective formation of disulfide bonds in cysteine‐rich peptides. The directed regioselective synthesis of human hepcidin, which contains four disulfide bonds, was undertaken and led to a high‐resolution NMR structure under more physiologically relevant conditions than previously. Conversely, hepcidin synthesized with the formerly assigned vicinal disulfide‐bond connectivity displayed significant conformational heterogeneity under similar conditions. The two synthetic forms of human hepcidin induced ferroportin internalization with apparent EC₅₀ values of 2.0 (native fold, 1 ) and 4.4 nM (non‐native fold, 2 ), with 2 undergoing isomerization to 1 in the presence of ferroportin expressing cells.     

Melt‐compounded nanocomposites of titanium dioxide atomic‐layer‐deposition‐coated polyamide and polystyrene powders

Polyamide and polystyrene particles were coated with titanium dioxide films by atomic layer deposition (ALD) and then melt‐compounded to form polymer nanocomposites. The rheological properties of the ALD‐created nanocomposite materials were characterized with a melt flow indexer, a melt flow spiral mould, and a rotational rheometer. The results suggest that the melt flow properties of polyamide nanocomposites were markedly better than those of pure polyamide and polystyrene nanocomposites. Such behavior was shown to originate in an uncontrollable decrease in the polyamide molecular weight, likely affected by a high thin‐film impurity content, as shown in gel permeation chromatography (GPC) and scanning electron microscope (SEM) equipped with an energy‐dispersive spectrometer. Transmission electron microscope image showed that a thin film grew on both studied polymer particles, and that subsequent melt‐compounding was successful, producing well dispersed ribbon‐like titanium dioxide with the titanium dioxide filler content ranging from 0.06 to 1.12 wt%. Even though we used nanofillers with a high aspect ratio, they had only a minor effect on the tensile and flexural properties of the polystyrene nanocomposites. The mechanical behavior of polyamide nanocomposites was more complex because of the molecular weight degradation. Our approach here to form polymeric nanocomposites is one way to tailor ceramic nanofillers and form homogenous polymer nanocomposites with minimal work‐related risks in handling powder form nanofillers. However, further research is needed to gauge the commercial potential of ALD‐created nanocomposite materials. Copyright © 2011 John Wiley & Sons, Ltd.     

Bisarylmaleimides & the Corresponding Indolocarbazoles as Kinase Inhibitors

Cyclin dependent kinases (CDKs) have recently raised considerable attention because of their central role in the regulation of cell cycle progression. A high incidence of genetic mutation of CDK substrates and deregulation of CDK modulators were found in a number of disease states, particularly in cancer. A novel series of unsymmetrical substituted indolocarbazoles were synthesized and their kinase inhibitory capability was evaluated in vitro. 6-Substituted indolocarbazoles were found to b…     

<Emphasis Type="Italic">Rhodobacter capsulatus</Emphasis> porphobilinogen synthase,a high activity metal ion independent hexamer

Background  

The enzyme porphobilinogen synthase (PBGS), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. This paper reports new information on the metal ion independence and quaternary structure of PBGS from the photosynthetic bacterium Rhodobacter capsulatus.