Molecular structure and conformation of cis-1,3- dichloro-1-propene as determined by gas phase electron diffraction

The molecular structure and conformation of cis-1,3-dichloro-1-propene have been determined by gas phase electron diffraction at a nozzle temperature of 90°C. The molecule exists in a form in which the chlorine atom of the methyl group and the carbon-carbon double bond are gauche to one another. The results for the distance (r_g) and angle (∠_α) parameters are: r(C-H) = 1.078(10)Å, r(CC) = 1.340(5)Å, r(C-C) = 1.508(7)Å, r( =C-Cl) = 1.762(3)Å, r(C-Cl) = 1.806(3)Å, ∠Cl-C-C = 111.7°(1.8), ∠(CC-C) = 125.5°(1.5), ∠Cl-CC = 124.6°(1.6) and ∠H-C-Cl = 111°(5). The torsion-sensitive distances close to the gauche form can be approximated using a dynamic model with a quartic double minimum potential function of the form V(Φ) = V₀[1 + ($\text{Φ}\text{Φ}{}_0$⁴ - 2($\text{Φ}\text{Φ}{}_0$)²], where V_o = 1.1(8) kcal mol^?1 and Φ₀ = 56°(5) (Φ = 0 corresponds to the anti form).     

Microbial pretreatment of biomass

Typical pretreatment requires high-energy (steam and electricity) and corrosion-resistant, high-pressure reactors. A review of the literature suggests that fungal pretreatment could potentially lower the severity requirements of acid, temperature and time. These reductions in severity are also expected to result in less biomass degradation and consequently lower inhibitor concentrations compared to conventional thermochemical pretreatment. Furthermore, potential advantages of fungal pretreatment of agricultural residues, such as corn stover, are suggested by its effectiveness in improving the cellulose digestibility of many types of forage fiber and agricultural wastes. Our preliminary tests show a three- to five-fold improvement in enzymatic cellulose digestibility of corn stover after pretreatment with Cyathus stercoreus; and a ten- to 100-fold reduction in shear force needed to obtain the same shear rate of 3.2 to 7 rev/s, respectively, after pretreatment with Phanerochaete chrysosporium.     

A practical route to 3'-amino-3'-deoxyadenosine derivatives and puromycin analogues

3'-aminoacylamino-3'-deoxyadenosines, analogues of the antibiotic puromycin, have been synthesized from adenosine. They key 3'-azido derivative 10 was obtained through a 3'-oxidation/reduction/substitution procedure. A modified purification protocol on a larger scale was developed for the oxidation step using the Garegg reagent. The coupling reaction between an Fmoc-l-amino acid and the fully protected form of 3'-amino-3'-deoxyadenosine 11 furnished the aminoacylated compounds 12 in high yields. The puromycin analogues were obtained in 10 steps and up to 23% (14c) overall yield.     

Effects of Plant Elicitors on Growth and Gypenosides Biosynthesis in Cell Culture of Giao co lam (Gynostemma pentaphyllum)

Giao co lam (Gynostemma pentaphyllum (Thunb.) Makino) is used in Northeast and Southeast Asia countries for the treatment of various diseases, including hepatitis, diabetes, and cardiovascular disease. G. pentaphyllum saponins (gypenosides) are the major components responsible for the pharmacological activities. In this study, different concentrations of abiotic (25–200 μM methyl jasmonate-MeJA and salicylic acid-SA) or biotic elicitors (1–5 g/L yeast extract-YE and Fusarium biomass) were used as plant elicitors, in order to investigate their influences on cell growth and gypenosides accumulation in G. pentaphyllum suspension cells. Suspension cells were grown on a MS medium containing 2.0 mg/L KIN and 0.5 mg/L IBA, with initial inoculum sizes of 3 g and shaking speeds of 120 rpm for 18 days. Gypenoside and Rb1 contents were measured by colorimetric and HPLC methods. Among three elicitors, SA was suitable for gypenosides accumulation in individual treatment. The cell biomass had the same values in elicitated and control suspension cells. Gypenosides content in cells treated with 100 μM salicylic acid after 6 days of culture reached a maximum value of 79.721 mg gypenoside/g dry biomass (including 0.093 mg ginsenoside Rb1/mg dry weight), which was 2.18-folds higher than that of the natural product. The elicitation promises an efficiency strategy for the production gypenosides in Gynostemma pentaphyllum suspension cells.     

A one-pot synthesis of 3-substituted-5-carbonylmethyl-1,2,4-oxadiazoles from β-keto esters and amidoximes under solvent-free conditions

Herein we report a high yielding one-pot ‘green’ synthesis of 3-substituted-5-carbonylmethyl-1,2,4-oxadiazoles from readily available β-keto esters and amidoximes under simple and convenient solvent-free conditions. No additional base is needed. The reaction likely goes through an acyl ketene intermediate.     

Stability criteria for set control differential equations

The existence and comparison results on solutions of set control differential equation were studied in [N.D. Phu, T.T. Tung, Some results on sheaf-solutions of sheaf set control problems, Nonlinear Analysis 67 (2007) 1309–1315]. In this paper, we present the stability criteria for solutions of set control differential equation.     

Efficient synthesis of tetrahydroquinolinones by acetic acid-mediated formal [3+3] cycloaddition

Abstract  

A simple and efficient method to synthesize a variety of tetrahydroquinolinones was successfully achieved by reacting various β-enaminones with several α,β-unsaturated aldehydes. This strategy can be viewed as a Br?nsted acid-mediated formal [3+3] cycloaddition.     

Mixed-valence uranium germanate and silicate: Cs(x)(U(V)O)(U(IV/V)O)2(Ge2O7)2 (x = 3.18) and Cs4(U(V)O)(U(IV/V)O)2(Si2O7)2

A new mixed-valence uranium germanate and the silicate analogue have been synthesized under hydrothermal conditions at 600 °C and 165 MPa. Their crystal structures contain infinite -U(V)-O-U(IV/V)-O-U(IV/V)-O-U(V)- chains that are connected by Ge(2)O(7) or Si(2)O(7) groups to form a 3D framework with six-ring channels where the Cs(+) cations are located. Two of the Cs sites in the germanate are partially occupied. Bond-valence-sum calculation and an U 4f X-ray photoelectron spectroscopy study confirm the valence states of the uranium.