XPS study of potassium-promoted molybdenum carbides for mixed alcohols synthesis via CO hydrogenation

The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both β-Mo_2C and α-MoC_(1-x) pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied. XPS results revealed that the content of surface Mo and its valence distribution between β-Mo_2C and α-MoC_(1-x) were quite different. Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over β-Mo_2C. Potassium had strong electronic effect on β-Mo_2C, which led to a higher Mo~(4+) content. On the contrary, potassium had little electronic effect on α-MoC_(1-x), and K-Mo interaction was weak. Therefore, Mo~0 and Mo~(2+) became the dominant species on the catalyst surface, and the Mo~(4+) content showed almost no increase as the pretreatment temperature enhanced. In terms of catalytic performance of molybdenum carbides, the increase in Mo~0 most likely explained the increase in hydrocarbon selectivity, yet Mo~(4+) might be responsible for the alcohols synthesis.     

New-generation biomedical materials: Peptide dendrimers and their application in biomedicine

Peptide dendrimers are attractive synthetic polymers and have been widely used as a new generation of biomaterials in recent years. Peptide dendrimers, as well as general dendrimers, may be synthesized to reach nano sizes, and display well-defined architectures, highly-branched structures, high density of functional terminal groups, and controllable molecular weights. On the other hand, peptide dendrimers have properties similar to proteins and some special characteristics, such as good biocompatibility, water solubility and resistance to proteolytic digestion. Due to these advantages, peptide dendrimers have received considerable attention in biomedicine. This review focuses on the development of peptide dendrimers with emphasis on their applications both in diagnostics and in therapy.     

Structure,biological and electrochemical studies of transition metal complexes from N,S,N′ donor ligand 8-(2-pyridinylmethylthio)quinoline

The semirigid tridentate 8-(2-pyridinylmethylthio)quinoline ligand (Q1) is shown to form the structurally characterized transition metal complexes [Cu(Q1)Cl₂] (1), [Co(Q1)(NO₃)₂] (2), [Cd(Q1)(NO₃)₂] (3), [Cd(Q1)I₂] (4). [Cu(Q1)₂](BF₄)₂·(H₂O)₂ (5), [Cu(Q1)₂](ClO₄)₂·(CH₃COCH₃)₂ (6), [Zn(Q1)₂](ClO₄)₂(H₂O)₂ (7), [Cd₂(Q1)₂Br₄] (8), [Ag₂(Q1)₂(ClO₄)₂] (9), and [Ag₂(Q1)₂(NO₃)₂] (10). Four types of structures have been observed: ML-type in complexes 1–4, in which the anions Cl⁻, NO₃⁻ or I⁻ also participate in the coordination; ML₂⁻ type in complexes 5–7 without direct coordination of the anions BF₄⁻ or ClO₄⁻ and with more (Cu²⁺) or less (Zn²⁺) distorted bis-fac coordinated Q1; M₂L₂-type in complex 8, in which two Br⁻ ions act as bridges between two metal ions; and M₂(μ-L)₂-type in complexes 9 and 10, in which the ligand bridges two anion binding and Ag–Ag bonded ions. Depending on electron configuration and size, different coordination patterns are observed with the bonds from the metal ions to N_pyridyl longer or shorter than those to N_quinoline. Typically Q1 acts as a facially coordinating tridentate chelate ligand except for the compounds 9 and 10 with low-coordinate silver(I). Except for 6 and 8, the complexes exhibit distinct constraining effects against both G(+) and G(-) bacteria. Complexes 1, 3, 4, 5, 7 have considerable antifungal activities and complexes 1, 5, 7, and 10 show selective effects to restrain certain botanic bacteria. Electrochemical studies show quasi-reversible reduction behavior for the copper(II) complexes 1, 5 and 6.     

Highly enantioselective epoxidation of alpha,beta-unsaturated esters by chiral dioxirane

This paper describes a highly enantioselective epoxidation of alpha,beta-unsaturated esters using the fructose-derived ketone 2 as catalyst and Oxone as oxidant. High ee's have been obtained for a number of trans and trisubstituted substrates (82-98% ee). The results described show that it is feasible for dioxiranes to effectively epoxidize electron-deficient olefins with high ee's.     

Facile Total Synthesis of (±)‐Nimbiol

A facile total synthesis of (±)‐nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a , an improved oxidation system of CrO₃/H₂O/HOAc/NaOAc was used.     

Comparative study of hollow-fiber liquid-phase micro-extraction and an aqueous two-phase system for determination of phytohormones in soil

Two methods, hollow-fiber liquid-phase micro-extraction (HF-LPME) and an aqueous two-phase system (ATPS), have been systematically optimized and compared for extraction and determination of phytohormones in soil by high-performance liquid chromatography (HPLC). The effects on extraction of conditions including solvent type and volume, extraction time, temperature, and amount of salt were evaluated. It was shown that ATPS was superior to HF-LPME for determination of paclobutrazol and uniconazole under the optimum conditions. The limits of detection (LODs) of ATPS were 0.002 μg g(-1) for uniconazole and 0.01 μg g(-1) for paclobutrazol, whereas LODs of HF-LPME were 0.005 μg g(-1) and 0.03 μg g(-1), respectively. Relative standard deviations (RSDs, n=5) and recovery were in the range 1.7-5.3 % and 86-102 %, respectively, for ATPS and 6.7-7.9 % and 40-60 % for HF-LPME. In addition, the advantages of ATPS were shorter extraction time, suitable for simultaneous pretreatment of batches of samples, and higher extraction capacity. ATPS was therefore applied to the determination of paclobutrazol and uniconazole in real soil samples. Uniconazole was detected in all the samples analyzed whereas paclobutrazol was not found.     

Synthesis and biological evaluation of new ligustrazine derivatives as anti-tumor agents

To discover new anti-cancer agents with multi-effect and low toxicity, a series of ligustrazine derivatives were synthesized using several effective anti-tumor ingredients of Shiquandabu Wan as starting materials. Our idea was enlightened by the "combination principle" in drug discovery. The ligustrazine derivatives' anti-tumor activities were evaluated on the HCT-8, Bel-7402, BGC-823, A-549 and A2780 human cancer cell lines. In addition the angiogenesis activities were valued by the chick chorioallantoic membrane (CAM) assay. 1,7-bis(4-(3,5,6-Trimethylpyrazin-2-yl)-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (4) and 3 α,12 α-dihydroxy-5β-dholanic acid-3,5,6-trimethylpyrazin-2-methyl ester (5) not only displayed antiproliferative activities on these cancer cells, but also dramatically suppressed normal angiogenesis in CAM. The LD?? value of the compound 5 exceeded 3.0 g/kg by oral administration in mice.     

A new lignan from Oxytropis myriophylla

The 70% alcohol extract of Oxytropis myriophylla (PALL.) DC. (Leguminosae) exhibited high radical scavenging activity (IC(50) value: 88.0?μg?mL(-1) and 86.7?μg?mL(-1)) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays. Further chemical investigation led the isolation of one new lignan, namely myriophylloside G (1), together with three known compounds. Their structural elucidations of all the compounds were based on extensive spectroscopic methods, including HRESIMS and 2D NMR experiments (HSQC, HMBC and (1)H-(1)HCOSY) and by comparison with reference values.     

Clean,One‐Pot Synthesis of Naphthopyran Derivatives in Aqueous Media

A general and practical one‐pot synthesis of naphthopyran derivatives using hexadecyltrimethylammonium bromide (HTMAB) as catalyst (10 mol%) is described. This method provides several advantages such as neutral conditions, high yields and simple workup procedure. The catalyst is low cost, facile, active, environmentally friendly, and reusable. In addition, water is chosen as a green solvent.