Synthesis of (arylselanyl)- and (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines via a copper-catalyzed multicomponent reaction

An efficient copper-catalyzed multicomponent reaction was developed for the synthesis of (arylselanyl)- or (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines. The products were obtained in moderate to excellent yields via the reaction of o-phenylenediamine, 2-azidobenzaldehyde and different arylchalcogenyl alkynes using catalytic copper iodide in 1,4-dioxane at 100?°C. The reactions tolerated a range of substituents on the arylchalcogenyl alkynes and proved to be an efficient methodology for the combinatorial synthesis of new selenium or sulfur-containing triazonine derivatives.     

A new isoflavone glycoside from Ceiba pentandra (L.) Gaertner

From the 80% EtOH extract of the bark of Ceiba pentandra (L.) Gaertner, a new isoflavone glycoside was isolated along with known isoflavones, vavain and vavain glucoside. The structure was elucidated by spectroscopic analysis as 5-hydroxy-7,4',5'-trimethoxyisoflavone 3'-O-alpha-L-arabinofuranosyl(1-->6)-beta-D-glucopyranoside.     

Stereoselective preparation of conjugated E-enynes from E-vinylic tellurides and terminal alkynes via Sonogashira cross-coupling

E-Vinylic tellurides undergo a direct cross-coupling reaction with terminal alkynes in the presence of palladium(II)/CuI in Et(3)N at room temperature to give E-enynes in good yields. The methodology represents a general and efficient protocol for carrying out the synthesis of E-enynes under mild conditions with complete retention of configuration.     

Analysis of methylglyoxal in water and biological matrices by capillary zone electrophoresis with diode array detection

We describe a new method for the determination of methylglyoxal in water and biological matrices, using o-phenylenediamine as derivatizing agent and solid-phase extraction followed by capillary zone electrophoresis with diode array detection. 25 mM sodium phosphate running buffers at pH 2.2, 30 kV, and 25 degrees C allowed the best instrumental conditions for the optimum separation of methylglyoxal in a suitable analytical time (< 10 min), using an uncoated fused-silica capillary of 75 microm inner diameter and an effective length of 45.1 cm with an extended light path and the wavelength set to 200 nm. Under optimized instrumental conditions, good reproducibility of the migration time (< 1.1%), precision (< 5%), an excellent linear dynamic range from 0.1 to 3.6 mg/L (r(2) = 0.9997), and low limits of detection (7.2 microg/L) were obtained for methylglyoxal measurements, using the internal standard methodology. Assays on laboratory-spiked tap and ground water samples allowed a remarkable accuracy, presenting yields of 95.0 +/- 4.3 and 94.0 +/- 1.1%, respectively, and good performance to determine methylglyoxal in beer and yeast cells suspensions matrices was also obtained at trace level. The present methodology is a cost-effective alternative for routine quality control analysis, showing to be reliable, sensitive, and with a low sample volume requirement to monitor methylglyoxal in water and biological matrices.     

Synthesis and characterization of hybrids derived from vermiculite chloropropyl and aliphatic diamines

Silylation of vermiculite surface with organosilane (H₃CO)₃SiR, being R is the corresponding organic moieties –CH₂CH₂CH₂Cl, were carried out to yield organofunctionalized nanomaterial, named as VCl. The product reacted subsequently with three aliphatic diamines H₂N (CH₂)_nNH₂ (n=2, 4 and 6). The new hybrids were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction and thermogravimetry. The grafting chloro derivates onto surface amounted to 2.1 mmol g^–1. The incorporation of alkyl amines was more effective for butyl>ethylene>hexyldiamines. The sequence is in agreement with thermogravimetry and elemental analysis data.     

Monte-Carlo simulation of stochastic differential systems — a geometrical approach

We develop some numerical schemes for d$d$-dimensional stochastic differential equations derived from Milstein approximations of diffusions which are obtained by lifting the solutions of the stochastic differential equations to higher dimensional spaces using geometrical tools, in the line of the work [A.B. Cruzeiro, P. Malliavin, A. Thalmaier, Geometrization of Monte-Carlo numerical analysis of an elliptic operator: Strong approximation, C. R. Acad. Sci. Paris, Ser. I 338 (2004) 481–486].