Asymmetric synthesis of 1-deoxyazasugars from chiral aziridines

A general and facile synthesis of enantiopure 1-deoxyazasugars was achieved from stereoselective dihydroxylation of a common synthetic intermediate, piperidine ring fused oxazolidin-2-one, originating from a commercially available starting substrate, chiral aziridine-2-carboxylate, in high yields.     

Pregnane and pregnane tetraglycoside from Marsdenia roylei

Pregnane oligoglycoside, namely roylinine, and a pregnane derivative, namely marsgenin, have been isolated from chloroform-soluble extract of dried stem of Marsdenia roylei, and their structures were determined using 1H-NMR, 13C-NMR, 1H-1H COSY, HSQC, TOCSY and FABMS spectral techniques as well as chemical degradation and derivatisation.     

微极流体蠕动泵经由滑移边界管道输送的Stokes流动

计及管道边界条件滑移的影响,研究微极流体蠕动泵,经由圆柱形管道输运的Stokes流动.壁面运动的控制方程为正弦波方程.使用润滑理论,得到了轴向速度、微转动向量、流函数、压力梯度、摩擦力和机械效率的解析数值解.用图形表示出构成参数,如像耦合参数、微极参数和表征蠕流泵特性的滑移参数、摩擦力和俘获现象的影响.数值计算表明,当耦合参数较大时,需要蠕动泵的压力更大,而微极参数和滑移参数正相反.俘获团块的大小随耦合参数和微极参数的减小而缩小,而随滑移参数的增大而缩小.     

Synthesis of novel quinoline analogues of nimesulide: An unusual observation

Reduction of nimesulide followed by treating the N‐acyl derivative of resulting arylamine with Vilsmeier‐Haack reagent provided novel 2‐chloro‐3‐formylquinoline derivatives. The construction of quinoline ring using Vilsmeier‐Haack reagent afforded an unexpected compound, N‐(2‐chloro‐3‐formyl‐7‐phenoxy quinolin‐6‐yl)formamide, in addition to the expected product. The structure of this unexpected quinoline derivative was established via single‐crystal X‐ray analysis and its formation could be explained by an unprecedented N‐S bond cleavage under Vilsmeier‐Haack reaction conditions. The 2‐chloro‐3‐formylquinoline derivatives obtained were converted to a number of corresponding Schiff bases with potential pharmacological importance. J. Heterocyclic Chem., 2011.     

Simple one‐pot conversion of organic compounds by hydrogen peroxide activated by ruthenium(III) chloride: organic conversions by hydrogen peroxide in the presence of ruthenium(III)

The aromatic compounds p‐nitrobenzaldehyde, p‐hydroxybenzaldehyde, naphthalene, toluene, catechol, quinol, aniline and toluidine dissolved in aqueous acetic acid or aqueous medium were oxidized in quantitative to good yields by 50% H₂O₂ in the presence of traces of RuCl₃ (～10^?8 mol; substrate/catalyst ratio 1488:1 to 341 250:1). Conditions for highest yields, in the most economical way, were obtained. Higher catalyst concentrations decrease the yield. Oxidation in aromatic aldehydes is selective at the aldehydic group only. In the case of hydrocarbons, oxidation results in the introduction of a hydroxyl group with >85% (in the case of toluene) selectivity for the ortho position. Formation of low‐molecular‐weight polyaniline was reduced to 10%, along with 90% formation of higher molecular weight polyaniline. In this new, simple and economical method, which is environmentally safe and requires less time, oxo‐centered carboxylate species of ruthenium(III) in acetic acid medium and hydrated ruthenium(III) chloride in aqueous medium probably catalyze the oxidation. Copyright © 2005 John Wiley & Sons, Ltd.     

The Quantum-Classical Comparison of the Arrival-Time Distribution Through the Probability Current

We consider the arrival time distribution defined through the quantum probability current for a Gaussian wave packet representing free particles in quantum mechanics in order to explore the issue of the classical limit of arrival time. We formulate the classical analogue of the arrival time distribution for an ensemble of free particles represented by a phase space distribution function evolving under the classical Liouville's equation. The classical probability current so constructed matches with the quantum probability current in the limit of minimum uncertainty. Further, it is possible to show in general that smooth transitions from the quantum mechanical probability current and the mean arrival time to their respective classical values are obtained in the limit of large mass of the particles.     

A unique method for reducing losses of bends in dielectric optical wave guide

The dielectric optical wave guide is finding growing attention at millimeter wave frequencies. However the dielectric optical waveguide radiates at bends and thus transmission loss increases. These radiations are in the outword direction of bends. This output radiation at output bends arises due to change in phase velocities of the propagating wave at the centre of the dielectric guide and the phase velocity at the outer surface of the dielectric guide. A unique methiod is suggested to avoid these radiation losses.Experimental results are also shown at microwave frequencies.     

Novel electron transfer mechanism in lithium alanate reduction of benzylic halides

Occurrence of a new electron transfer mechanism in the LiAlH₄ reduction of 9-chloromethylanthrancene, diphenylchloromethane and 9-bromofluorene is demonstrated. Alanate anion serves as a source of electrons and hydrogen atoms.