A Concise Flow Synthesis of Efavirenz

Efavirenz is an essential medicine for the treatment of HIV, which is still inaccessible to millions of people worldwide. A novel, semi‐continuous process provides rac‐Efavirenz with an overall yield of 45 %. This streamlined proof‐of‐principle synthesis relies on the efficient copper‐catalyzed formation of an aryl isocyanate and a subsequent intramolecular cyclization to install the carbamate core of Efavirenz in one step. The three‐step method represents the shortest synthesis of this life‐saving drug to date.     

Mixed Ca/Sr salt forms of salicylic acid: tuning structure and aqueous solubility

Ten isostructural single‐crystal diffraction studies of mixed cation Ca/Sr salt forms of the salicylate anion are presented, namely catena‐poly[[diaquacalcium(II)/strontium(II)]‐bis(μ₂‐2‐hydroxybenzoato)], [Ca_1–xSr_x(C₇H₅O₃)₂(H₂O)₂]_n, where x = 0, 0.041, 0.083, 0.165, 0.306, 0.529, 0.632, 0.789, 0.835 and 1. The structure of an isostructural Sr/Ba species, namely catena‐poly[[diaquastrontium(II)/barium(II)]‐bis(μ₂‐2‐hydroxybenzoato)], [Sr_0.729Ba_0.271(C₇H₅O₃)₂(H₂O)₂], is also described. The Ca/Sr structures form a series where, with increasing Sr content, the unit cell expands in both the crystallographic a and c directions (by 1.80 and 3.18%, respectively), but contracts slightly in the b direction (−0.31%). The largest percentage structural expansion lies parallel to the direction of propagation of the one‐dimensional coordination polymer that is the primary structural feature. This structural expansion is thus associated with increased M—O distances. Aqueous solubility measurements show that solubility generally increases with increasing Sr content. Thus, tuning the composition of these mixed counter‐ion salt forms leads to systematic structural changes and allows solubility to be tuned to values between those for the pure Ca and Sr species.     

双苯氟嗪盐酸盐和苯甲酸的共晶制备和谱学分析

药物共晶是改善药物活性成分(API)的物理化学特性的新技术和新思维,具有很大的应用潜力。本实验采用研磨法制备了双苯氟嗪盐酸盐(DF-HCl)和苯甲酸的共晶,应用红外光谱(IR)、拉曼光谱(Raman)、差示扫描量热分析(DSC)、X射线衍射(XRD)和太赫兹光谱(THz)对共晶进行了表征。结果表明:双苯氟嗪盐酸盐与苯甲酸之间形成共晶分子,太赫兹谱的研究进一步表明两种分子之间有氢键形成。     

Experimental and theoretical study of crude oil pretreatment using low-frequency ultrasonic waves

In this work, an ultrasound experimental setup was designed to investigate the feasibility of using low-frequency ultrasonic waves as a substitute to reduce the consumption of chemical demulsifiers in the pretreatment of crude oil. The experiments were planned to study the effects of irradiation time, ultrasonic field intensity and initial water content on the efficiency of separation. The results of experiments showed that by selecting a proper irradiation time and field intensity, it is possible to decrease the usage of demulsifiers by 50%. Moreover, a population balance model was proposed to explicate the experimental data. A hybrid coalescence model was developed to determine the frequency of aggregation. The parameters of the model were estimated by linear regression. The parameter estimation was performed using a parallel execution of the particle swarm optimization algorithm. The results of the model showed a decent agreement with the experimental data.     

Intermolecular interactions and disorder in six isostructural celecoxib solvates

Six isostructural crystalline solvates of the active pharmaceutical ingredient celecoxib {4‐[5‐(4‐methylphenyl)‐3‐(trifluoromethyl)pyrazol‐1‐yl]benzenesulfonamide; C₁₇H₁₄F₃N₃O₂S} are described, containing dimethylformamide (DMF, C₃H₇NO, 1 ), dimethylacetamide (DMA, C₄H₉NO, 2 ), N‐methylpyrrolidin‐2‐one (NMP, C₅H₉NO, 3 ), tetramethylurea (TMU, C₅H₁₂N₂O, 4 ), 1,3‐dimethyl‐3,4,5,6‐tetrahydropyrimidin‐2(1H)‐one (DMPU, C₆H₁₂N₂O, 5 ) or dimethyl sulfoxide (DMSO, C₂H₆OS, 6 ). The host celecoxib structure contains one‐dimensional channel voids accommodating the solvent molecules, which accept hydrogen bonds from the NH₂ groups of two celecoxib molecules. The solvent binding sites have local twofold rotation symmetry, which is consistent with the point symmetry of the solvent molecule in 4 and 5 , but introduces orientational disorder for the solvent molecules in 1 , 2 , 3 and 6 . Despite the isostructurality of 1 – 6 , the unit‐cell volume and solvent‐accessible void space show significant variation. In particular, 4 and 5 show an enlarged and skewed unit cell, which can be attributed to a specific interaction between an N—CH₃ group in the solvent molecule and the toluene group of celecoxib. Intermolecular interaction energies calculated using the PIXEL method show that the total interaction energy between the celecoxib and solvent molecules is broadly correlated with the molecular volume of the solvent, except in 6 , where the increased polarity of the S=O bond leads to greater overall stabilization compared to the similarly‐sized DMF molecule in 1 . In the structures showing disorder, the most stable orientations of the solvent molecules make C—H…O contacts to the S=O groups of celecoxib.     

An efficient and extensible format,library, and API for binary trajectory data from molecular simulations

Molecular dynamics simulations is an important application in theoretical chemistry, and with the large high‐performance computing resources available today the programs also generate huge amounts of output data. In particular in life sciences, with complex biomolecules such as proteins, simulation projects regularly deal with several terabytes of data. Apart from the need for more cost‐efficient storage, it is increasingly important to be able to archive data, secure the integrity against disk or file transfer errors, to provide rapid access, and facilitate exchange of data through open interfaces. There is already a whole range of different formats used, but few if any of them (including our previous ones) fulfill all these goals. To address these shortcomings, we present “Trajectory Next Generation” (TNG)—a flexible but highly optimized and efficient file format designed with interoperability in mind. TNG both provides state‐of‐the‐art multiframe compression as well as a container framework that will make it possible to extend it with new compression algorithms without modifications in programs using it. TNG will be the new file format in the next major release of the GROMACS package, but it has been implemented as a separate library and API with liberal licensing to enable wide adoption both in academic and commercial codes. © 2013 Wiley Periodicals, Inc.     

Estimation of crude oil grade using time-resolved fluorescence spectra

Time-resolved fluorescence (TRF) spectra of six crude oils from the eastern province of Saudi Arabia were excited using a pulsed laser radiation at 250 nm and measured at specific time gates (TG) within the leading and trailing edges of the laser temporal pulse. The spectra showed the presence of a shoulder near 380 nm that systematically decreased in intensity from high-grade to low-grade crudes, and also from earlier to later TGs. The intensities of these shoulders are shown to be useful in estimating the grades of crude oils, particularly when the TRF spectra are measured at TGs within the leading edge of the laser temporal pulse. Contour diagrams depicting the shapes of the TRF spectra as function of TG (within the leading and trailing edges) are also presented to serve as true fingerprints of the crudes.     

基于Android系统的手机恶意软件检测模型

为提高手机应用软件的安全性,提出一种基于Android系统的手机恶意软件检测模型。模型利用数据挖掘的方法对恶意软件中的敏感API调用进行数据挖掘,进而得到恶意软件检测规则;针对检测规则在检测非恶意软件时,产生较高误报率的问题,设计了加权FP-growth关联规则挖掘算法,算法在数据挖掘的两个步骤中,对敏感API调用加权,利用支持度阈值去除一些出现次数频繁而权重小的规则,降低了非恶意软件的误报率。实验结果表明,模型对恶意软件检测率达到81.7%,非恶意软件的检错率降低到11.3%。     

Determination of Phosphorus in Crude Oil and Middle Distillate Petroleum Products by Inductively Coupled Plasma–Optical Emission Spectrometry

A method for the precise and accurate determination of phosphorus in crude oil and middle distillate petroleum products was developed using inductively coupled plasma–optical emission spectrometry to rapidly determine phosphorus as a control method. The presence of phosphorus is undesirable in petrochemical products as it complexes with other metals generating residues that interrupt normal operation of refineries. The presence of phosphorus may be due to some anti-fouling additives or the crude oils processed. Consequently, it is necessary to control the phosphorus present at trace levels in the crude oil and in process streams that present various densities and viscosities. The instrumental power, nebulizer flow, pump rate, read time, and the sample preparation conditions were optimized. The desired level of quantification for the petrochemical industry was achieved allowing the simultaneous analysis of diverse liquid petroleum products.