Ligand-free palladium-catalyzed intramolecular Heck reaction of secondary benzylic bromides

A facile ligand-free palladium-catalyzed intramolecular Heck reaction of β-hydrogen-containing secondary benzylic bromides was developed, which affords pyrroline derivatives with good regioselectivities.     

A facile process for the asymmetric synthesis of β-trifluoromethylated β-amino ketones via addition of ketone enolates to sulfinylimine

An efficient method for the asymmetric synthesis of β-trifluoromethylated β-amino ketones via addition of ketone-derivative enolates to trifluoromethylated sulfinylimine has been developed, with good chemical yields and excellent diastereoselectivities. This practical method was also proved to be suitable for large-scale preparation.     

Fabrication of doxorubicin functionalized gold nanorod probes for combined cancer imaging and drug delivery

A novel strategy was utilized to develop a stable probe based on thiolated poly(ethylene glycol) (SH-PEG) and polyacrylic acid (PAA) functionalized gold nanorods (GNRs), following the attachment of an anti-cancer drug, doxorubicin (DOX), to obtain PAA-PEG-GNRs@DOX assemblies. Importantly, the obtained probe as a novel drug-delivery and fluorescent imaging agent for simultaneous imaging of and drug delivery to prostate cancer cells has also been demonstrated. In addition to designing PAA-PEG-GNRs that passively target tumor cells for cancer-fighting drug therapy, GNRs are also regarded as hyperthermia agents for photokilling cancer cells, so that the tumor would be attacked on two fronts simultaneously.     

A new conformer of indium germanate InGe3O7.5(en): conformational polymorphism in germanate family

A new conformer of indium germanate InGe(3)O(7.5)(en) (denoted as δ-type), constructed with the flexible unit of In(2)Ge(6)O(15)N(2) was successfully prepared through a solvothermal method. The crystal data for the δ-type InGe(3)O(7.5)(en) are listed as follows: triclinic, space group P-1 (No.2), a = 7.826(4) ?, b = 8.287(3) ?, c = 9.224(4) ?, α = 71.887(17)°, β = 85.343(18)°, γ = 63.734(12)°, V = 508.64 ?(3), Z = 2. Four relevant conformers of indium germanate are compared with each other. The conformational polymorphism in the germanate family is reported for the first time.     

Through-space charge-transfer emitting biphenyls containing a boryl and an amino group at the o,o'-positions

A new class of organoboron compounds containing a boryl and an amino group at the o,o'-positions of biphenyls display bright through-space intramolecular charge transfer fluorescence owing to the close contact between the boryl and the amino groups. Binding of the fluoride ions results in the remarkable blue shift and color change of the fluorescence, enabling colorimetric and ratiometric fluoride ion sensing.     

Ir(I)-catalyzed enantioselective secondary sp3 C-H bond activation of 2-(alkylamino)pyridines with alkenes

A cationic Ir(I)-tolBINAP complex catalyzed an enantioselective C-C bond formation initiated by secondary sp(3) C-H bond cleavage adjacent to a nitrogen atom. The reaction of 2-(alkylamino)pyridines with various alkenes gave chiral amines in good yields with high enantiomeric excesses.     

Rubesanolides A and B: diterpenoids from Isodon rubescens

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.     

Predicting Fixation Tendencies of the H3N2 Influenza Virus by Free Energy Calculation

Influenza virus evolves to escape from immune system antibodies that bind to it. We used free energy calculations with Einstein crystals as reference states to calculate the difference of antibody binding free energy (ΔΔG) induced by amino acid substitution at each position in epitope B of the H3N2 influenza hemagglutinin, the key target for antibody. A substitution with positive ΔΔG value decreases the antibody binding constant. On average an uncharged to charged amino acid substitution generates the highest ΔΔG values. Also on average, substitutions between small amino acids generate ΔΔG values near to zero. The 21 sites in epitope B have varying expected free energy differences for a random substitution. Historical amino acid substitutions in epitope B for the A/Aichi/2/1968 strain of influenza A show that most fixed and temporarily circulating substitutions generate positive ΔΔG values. We propose that the observed pattern of H3N2 virus evolution is affected by the free energy landscape, the mapping from the free energy landscape to virus fitness landscape, and random genetic drift of the virus. Monte Carlo simulations of virus evolution are presented to support this view.     

Accurate analysis of trace pentachlorophenol in textiles by isotope dilution liquid chromatography-mass spectrometry

A highly accurate method for measuring pentachlorophenol (PCP) concentrations in textile samples was developed. This highly accurate method for the analysis of textile samples is valuable, given the inherent challenges associated with the complexity of the sample matrix. This method can be applied to certify the concentration of pentachlorophenol in textile CRMs. A measurement procedure based on isotope dilution liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed. Samples were pretreated with acid and then with n-hexane. Excellent precision was obtained. The validated concentration ranges for the method were 1.0-50 ng/g, the LOD was 1.0 ng/g, and the LOQ was 5.0 ng/g. The precision of this method is in the range of 0.80-1.40%. The method can trace to mass.     

Circular consecutive choosability of k‐choosable graphs

Let S(r) denote a circle of circumference r. The circular consecutive choosability ch_cc(G) of a graph G is the least real number t such that for any r≥χ_c(G), if each vertex v is assigned a closed interval L(v) of length t on S(r), then there is a circular r‐coloring f of G such that f(v)∈L(v). We investigate, for a graph, the relations between its circular consecutive choosability and choosability. It is proved that for any positive integer k, if a graph G is k‐choosable, then ch_cc(G)?k + 1 ? 1/k; moreover, the bound is sharp for k≥3. For k = 2, it is proved that if G is 2‐choosable then ch_cc(G)?2, while the equality holds if and only if G contains a cycle. In addition, we prove that there exist circular consecutive 2‐choosable graphs which are not 2‐choosable. In particular, it is shown that ch_cc(G) = 2 holds for all cycles and for K_{2, n} with n≥2. On the other hand, we prove that ch_cc(G)>2 holds for many generalized theta graphs. © 2011 Wiley Periodicals, Inc. J Graph Theory 67: 178‐197, 2011