环丙基乙炔的合成研究

以环丙基甲基酮为起始原料,五氯化磷为氯化试剂,采用先氯化后消除的工艺合成了依非韦伦关键中间体环丙基乙炔。针对二氯代物中间体(1,1-二氯乙基)环丙烷和一氯代物中间体(1-氯乙烯基)环丙烷消除反应活性的不同,分别在三乙胺和氢氧化钾存在下进行分步消除反应,对消除反应的实验条件进行了优化。得到优化的合成条件为:在3%吡啶(以环丙基甲基酮质量为基准,下同)、10～15℃下进行氯化反应;以三乙胺为碱,回流状态下进行一步消除反应;在KOH/DMSO体系中于110℃进行二步消除反应。在该条件下,以环丙基甲基酮计,环丙基乙炔单程收率可达49%。同时建立了三乙胺的回收套用工艺,进一步降低了成本,具有良好的工业化前景。     

Solubility and dissolution performances of spray-dried solid dispersion of Efavirenz in Soluplus

Abstract

Efavirenz (EFV), a first-line anti-HIV drug largely used as part of antiretroviral therapies, is practically insoluble in water and belongs to BCS class II (low solubility/high permeability). The aim of this study was to improve the solubility and dissolution performances of EFV by formulating an amorphous solid dispersion of the drug in polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (Soluplus^®) using spray-drying technique. To this purpose, spray-dried dispersions of EFV in Soluplus^® at different mass ratios (1:1.25, 1:7, 1:10) were prepared and characterized using particle size measurements, SEM, XRD, DSC, FTIR and Raman microscopy mapping. Solubility and dissolution were determined in different media. Stability was studied at accelerated conditions (40?°C/75% RH) and ambient conditions for 12 months. DSC and XRD analyses confirmed the EFV amorphous state. FTIR spectroscopy analyses revealed possible drug–polymer molecular interaction. Solubility and dissolution rate of EFV was enhanced remarkably in the developed spray-dried solid dispersions, as a function of the polymer concentration. Spray-drying was concluded to be a proper technique to formulate a physically stable dispersion of amorphous EFV in Soluplus^®, when protected from moisture.     

Glass transitions in binary drug + polymer systems

To evaluate miscibility, glass transition temperatures T_g have been determined for two binary polymer (Plasdone S-630 copovidone or Eudragit® E) + drug systems as a function of composition. Each polymer serves for encapsulation of the anti-HIV drug Efavirenz. In both systems the T_g vs. drug concentration diagrams are s-shaped. T_gs of Efavirenz + Plasdone mixtures with drug mass fraction below φ_drug = 0.6 are above linear values. This implies enhanced thermal and mechanical stability—an advantage for the drug encapsulation. In the other system, a strong negative deviation of T_gs is observed over the entire compositional range and explained by positive excess mixing volumes. Several equations are used to represent T_g vs. composition diagrams, but only one (Brostow et al. Mater Lett 2008; 62:3152) provides reliable results.     

Preparation of Efavirenz resinate by spray drying using response surface methodology and its physicochemical characterization for taste masking

Abstract

In the present study, taste masked drug–resin complex (DRC) of efavirenz (EFV) was prepared by spray drying technique. The DRC was then incorporated in to a fast dissolving tablet dosage form. EFV is antiretroviral agent of very bitter taste and low oral bioavailability. To investigate the influence of the independent variables on encapsulation efficiency (EE) as well as on the bitter taste of EFV, response surface methodology was employed. Ion-exchange resin (tulsion-335) and amount of solvent were selected as the independent variables while the EE was selected as the dependent variable. DRC was characterized for EE, X-ray diffraction, particle size distribution, Fourier transform infrared spectroscopy, surface morphology, and in vitro dissolution study. The spectrophotometric method was used for the evaluation of bitter taste of EFV. The EE was found to be 37–84%. The compressed tablets were evaluated for the hardness, Friability, wetting time, disintegration time and in vitro drug release studies. This study confirmed that complexation of the drug with an ion-exchange resin can effectively mask the bitter taste of the drug in combination with production of fast dissolving tablets.     

What do molecules do when we are not looking? State sequence analysis for stochastic chemical systems

Many biomolecular systems depend on orderly sequences of chemical transformations or reactions. Yet, the dynamics of single molecules or small-copy-number molecular systems are significantly stochastic. Here, we propose state sequence analysis—a new approach for predicting or visualizing the behaviour of stochastic molecular systems by computing maximum probability state sequences, based on initial conditions or boundary conditions. We demonstrate this approach by analysing the acquisition of drug-resistance mutations in the human immunodeficiency virus genome, which depends on rare events occurring on the time scale of years, and the stochastic opening and closing behaviour of a single sodium ion channel, which occurs on the time scale of milliseconds. In both cases, we find that our approach yields novel insights into the stochastic dynamical behaviour of these systems, including insights that are not correctly reproduced in standard time-discretization approaches to trajectory analysis.     

Factors influencing the erosion rate and the drug release kinetics from organogels designed as matrices for oral controlled release of a hydrophobic drug

Abstract

This article proposes solid-like systems from sunflower oil structured with a fibrillar network built by the assembly of 12-hydroxystearic acid (12-HSA), a gelator molecule for an oil phase. The resulting organogels were studied as oral controlled release formulations for a lipophilic drug, Efavirenz (EFV), dissolved in the oil. The effects of the gelator concentration on the thermal properties of the organogels were studied by Differential Scanning Calorimetry (DSC) and showed that drug incorporation did not change the sol–gel–sol transitions. The erosion and drug release kinetics from organogels under conventional (filling gelatin capsules) or multiparticulate (beads obtained by prilling) dosage forms were measured in simulated gastric and intestinal fluids. EFV release profiles were analyzed using model-dependent (curve-fitting) and independent approaches (Dissolution Efficiency DE). Korsmeyer–Peppas was the best fitting release kinetic model based on the goodness of fit, revealing a release mechanism from organogels loaded with EFV different from the simple drug diffusion release mechanism obtained from oily formulations. From organogels, EFV probably diffuses through an outer gel layer that erodes releasing oil droplets containing dissolved EFV into the aqueous medium.