Recent developments in the synthesis of zoanthamine alkaloids

This review provides a compilation of the most recent synthetic approaches and total syntheses of zoanthamine alkaloids, which are structurally unique heptacyclic marine natural products that display a range of interesting biological activities. This review is focused on synthetic methodologies for the construction of the three adjacent quaternary asymmetric carbon atoms on the cyclohexane ring (C-ring) of these compounds. The literature covered in this review dates from 2008 to the end of 2013.     

Recent developments in capillary electrophoresis and capillary electrochromatography of carbohydrate species

This review article is concerned with the recent developments in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of carbohydrates. The literature shows that CE possesses impressive potential in the analysis of carbohydrates. On the other hand, CEC has just started to show promise in the analysis of carbohydrates. Advances in separation and detection approaches of derivatized and underivatized carbohydrates are discussed based on the available literature. In addition, important applications are illustrated.     

Simultaneous spreading and evaporation: Recent developments

The recent progress in theoretical and experimental studies of simultaneous spreading and evaporation of liquid droplets on solid substrates is discussed for pure liquids including nanodroplets, nanosuspensions of inorganic particles (nanofluids) and surfactant solutions. Evaporation of both complete wetting and partial wetting liquids into a nonsaturated vapour atmosphere are considered. However, the main attention is paid to the case of partial wetting when the hysteresis of static contact angle takes place. In the case of complete wetting the spreading/evaporation process proceeds in two stages. A theory was suggested for this case and a good agreement with available experimental data was achieved. In the case of partial wetting the spreading/evaporation of a sessile droplet of pure liquid goes through four subsequent stages: (i) the initial stage, spreading, is relatively short (1–2 min) and therefore evaporation can be neglected during this stage; during the initial stage the contact angle reaches the value of advancing contact angle and the radius of the droplet base reaches its maximum value, (ii) the first stage of evaporation is characterised by the constant value of the radius of the droplet base; the value of the contact angle during the first stage decreases from static advancing to static receding contact angle; (iii) during the second stage of evaporation the contact angle remains constant and equal to its receding value, while the radius of the droplet base decreases; and (iv) at the third stage of evaporation both the contact angle and the radius of the droplet base decrease until the drop completely disappears. It has been shown theoretically and confirmed experimentally that during the first and second stages of evaporation the volume of droplet to power 2/3 decreases linearly with time. The universal dependence of the contact angle during the first stage and of the radius of the droplet base during the second stage on the reduced time has been derived theoretically and confirmed experimentally. The theory developed for pure liquids is applicable also to nanofluids, where a good agreement with the available experimental data has been found. However, in the case of evaporation of surfactant solutions the process deviates from the theoretical predictions for pure liquids at concentration below critical wetting concentration and is in agreement with the theoretical predictions at concentrations above it.     

Reproducibility in pyrolysis: Recent developments

Although it has been used as an analytical tool for decades, pyrolysis is still frequently ill-applied to the analysis of solid samples by gas chromatography. The question of reproducibility is fundamental to the utility of any analytical technique, and the practitioners of these techniques must investigate means of providing greater reproducibility. The question of reproducibility as it applies to the analysis of solid materials by pyrolysis-gas chromatography is discussed. Sources of non-reproducible results will be examined from three views: first considering irreproducibility introduced by the entire analytical scheme, including parts of the instrumentation not directly involved with the pyrolysis of the sample; second, concerning the actual pyrolysis of the sample by the pyrolyzer; and finally a look at some recent advances made to reduce or eliminate the sources of irreproducibility.     

Food oral processing: Recent developments and challenges

As the very first step of food consumption, food oral processing is not only of great importance to food intake and the following digestion and adsorption, but also provides the necessary sensory attributes that please the consumer. Starting from the first bite, to oral manipulation including mastication and transportation, until bolus formation and swallowing, food products undergo a variety of physical and biochemical changes over a wide range of time and length scales. A number of efforts had been made to uncover the mechanisms in each oral processing step; some of which are still poorly understood. This review covers some of the most recent progress made in the area of food oral processing, with an emphasis on eating and swallowing difficulties in the elderly and the corresponding model food development. It also includes the oral surface coating and lubrication and the dynamic textural perception during food oral processing. The authors hope that this will facilitate food scientists, psychologists, dentists and other clinical researchers to further understand and reveal the detailed controlling mechanisms and governing principles of food oral processing.     

Low-pressure gas chromatography: Recent trends and developments

In the past few years, low-pressure gas chromatography (LP-GC) has been applied for the fast analysis of various pollutants in different environmental and food matrices. A typical LP-GC set-up involves the use of a short microbore column (typically 0.5–1 m × 0.10 mm internal diameter) at the injector side connected with a zero dead-volume connector to a short megabore column (typically 10 m × 0.53 mm) to be used with higher gas velocities. This set-up maintains atmospheric injection conditions, while the analytical column is operated under low-pressure conditions that are compatible with mass-spectrometer analyzers. Although the use of LP-GC results in a loss of separation efficiency, it offers a 3–5-fold reduction in analysis time for organic compounds and thus increased sample throughput and enhancement of the signal-to-noise ratio leading to improved detection limits. Considering the significance of, and the potential interest in, this topic, this review briefly describes the concept of LP-GC. Furthermore, we explore recent developments and applications of LP-GC, with a focus on the use of various column systems and analyzers. Finally, we critically evaluate the prospects for, and the limitations of, LP-GC.     

Recent developments in chromatographic fingerprints from herbal products: set-up and data analysis

The use of chromatographic fingerprints from herbal products where the whole chromatographic profile is applied to evaluate the quality of the investigated product. In this paper, recent developments in the set-up and data analysis of chromatographic fingerprints for herbal products are discussed. First different set-ups for fingerprint development are reviewed. Prior to fingerprint development, a suitable sample preparation, e.g. extraction, should be considered. In a second instance, this review focuses on the data analysis with regards to the different applications of fingerprints. Usually, chemometric data pretreatment is necessary. This is discussed first, followed by a short overview of the data handling techniques used in the two main application areas of herbal fingerprints, i.e. quality assurance and classification or calibration. The quality assurance, which involves the identification and quality control of the herbal products, is reviewed, followed by the use of fingerprints in classification or modelling. The different application areas are illustrated and discussed with several case studies.     

The quaternary indole alkaloids from two Sumatran Lerchea species

The Sumatran forest plants Lerchea cf. bracteata and L. parviflora were found to contain alkaloids and their extract showed siginificant activity toward some testing pathogenic microbes. Isolation work on L.cf bracteata yielded known quaternary alkaloid N(b)-methylantirhine (2) while L. parviflora gave 5,6-dihydroflavopereirine (3).     

The superhydrophobicity of polymer surfaces: Recent developments

Superhydrophobicity is the extreme water repellence of highly textured surfaces. The field of superhydrophobicity research has reached a stage where huge numbers of candidate treatments have been proposed and jumps have been made in theoretically describing them. There now seems to be a move to more practical concerns and to considering the demands of individual applications instead of more general cases. With these developments, polymeric surfaces with their huge variety of properties have come to the fore and are fast becoming the material of choice for designing, developing, and producing superhydrophobic surfaces. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1203–1217, 2011     

Recent developments in cyanide detection: A review

The extreme toxicity of cyanide and environmental concerns from its continued industrial use continue to generate interest in facile and sensitive methods for cyanide detection. In recent years, there is also additional recognition of HCN toxicity from smoke inhalation and potential use of cyanide as a weapon of terrorism. This review summarizes the literature since 2005 on cyanide measurement in different matrices ranging from drinking water and wastewater, to cigarette smoke and exhaled breath to biological fluids like blood, urine and saliva. The dramatic increase in the number of publications on cyanide measurement is indicative of the great interest in this field not only from analytical chemists, but also researchers from diverse environmental, medical, forensic and clinical arena. The recent methods cover both established and emerging analytical disciplines and include naked eye visual detection, spectrophotometry/colorimetry, capillary electrophoresis with optical absorbance detection, fluorometry, chemiluminescence, near-infrared cavity ring down spectroscopy, atomic absorption spectrometry, electrochemical methods (potentiometry/amperometry/ion chromatography-pulsed amperometry), mass spectrometry (selected ion flow tube mass spectrometry, electrospray ionization mass spectrometry, gas chromatography-mass spectrometry), gas chromatography (nitrogen phosphorus detector, electron capture detector) and quartz crystal mass monitors.     

Recent developments on the fluorinase from Streptomyces cattleya

This is a summary of a lecture presented at the 100th Anniversary, Moissan Symposium in Paris on Friday, 10 November 2006. The lecture highlighted recent developments on the enzyme structure, mechanism and biotransformation prospects of the fluorinase enzyme identified in 2002 from the bacterium Streptomyces cattleya. Over-expression of the enzyme has allowed it to be used as a catalyst for ¹⁸F-incorporation during the synthesis of potential ligands for positron emission tomography (PET) applications.     

Lithium-ion battery separators: Recent developments and state of art

Lithium-ion battery separators are receiving increased consideration from the scientific community. Single-layer and multilayer separators are well-established technologies, and the materials used span from polyolefins to blends and composites of fluorinated polymers. The addition of ceramic nanoparticles and separator coatings improves thermal and mechanical properties, as well as electrolyte uptake and ionic conductivity. The state-of-art separators are actively involved in the cell chemistry through specific functional groups on their surface. Among the numerous properties, safety features and long cycle life are high-priority requirements for next-generation lithium-ion batteries.     

Chiral separations by capillary electrophoresis: Recent developments and applications

This paper provides an overview of the different classes of chiral selectors that are used in CE. The main properties of every class are described, together with the mechanism of enantioseparation. Newly introduced selectors are also discussed. Pharmaceutical and biomedical applications published from January 2004 till March 2005 are summarized.     

Recent trends and developments in pyrolysis-gas chromatography

Pyrolysis-gas chromatography (Py-GC) has become well established as a simple, quick and reliable analytical technique for a range of applications including the analysis of polymeric materials. Recent developments in Py-GC technology and instrumentation include laser pyrolysis and non-discriminating pyrolysis. Progress has also been made in the detection of low-level polymer additives with the use of novel Py-GC devices. Furthermore, it has been predicted that future advances in separation technology such as the use of comprehensive two-dimensional gas chromatography will further enhance the analytical scope of Py-GC.     

Syntheses of quinazoline-2,4-dione alkaloids and analogues from Mexican Zanthoxylum species

Quinazolinone and quinazolinedione derivatives are of considerable interest due to their wide array of pharmacological properties. In this paper we report the synthesis of ten quinazolinediones. The previous isolation of two of these compounds, namely 1-methyl-3-(2'-phenylethyl)-1H,3H-quinazoline-2,4-dione and 1-methyl-3-[2'-(4'- methoxyphenyl)ethyl]-lH,3H-quinazoline-2,4-dione, from the seed husks of Mexican Zanthoxylum species has been reported.     

Recent developments in the metal-catalyzed reactions of metallocarbenoids from propargylic esters

The transition-metal-catalyzed intramolecular cycloisomerization of propargylic carboxylates provides functionalized bicyclo[n.1.0]enol esters in a very diastereoselective manner and, depending on the structure, with partial or complete transfer of chirality from enantiomerically pure precursors. The subsequent methanolysis gives bicyclo[n.1.0] ketones, hence resulting in a very efficient two-step protocol for the syntheses of alpha,beta-unsaturated cyclopropyl ketones, key intermediates for the preparation of natural products. The results from mechanistic computational studies suggest that they probably proceed through cyclopropyl metallocarbenoids, formed by endo-cyclopropanation, that undergo a 1,2-acyl migration. Finally, the potential of the intermolecular reaction and the related pentannulation of propargylic esters bearing pendant aromatic rings are also discussed.     

Hyrtioseragamines A and B, new alkaloids from the sponge Hyrtios species

Two novel alkaloids with a furo[2,3-b]pyrazin-2(1H)-one moiety and a guanidino group, hyrtioseragamines A (1) and B (2), have been isolated from an Okinawan marine sponge Hyrtios species. The structures of 1 and 2 were elucidated on the basis of spectroscopic data and chemical conversions. Compounds 1 and 2 are the first natural products possessing a furo[2,3-b]pyrazine-related moiety.     

Nagelamides K and L, dimeric bromopyrrole alkaloids from sponge Agelas species

Two new dimeric bromopyrrole alkaloids, nagelamides K (1) and L (2), have been isolated from Okinawan marine sponges Agelas species, and the structures and stereochemistry were elucidated from spectroscopic data. Nagelamide K (1) is a bromopyrrole alkaloid possessing a rare piperidinoiminoimidazolone ring with an aminoimidazole ring and a taurine unit, while nagelamide L (2) is a unique dimeric bromopyrrole alkaloid containing an ester linkage. Nagelamides K (1) and L (2) exhibited antimicrobial activity.     

Low-temperature direct ammonia fuel cells: Recent developments and remaining challenges

Low-temperature direct ammonia fuel cells (DAFCs) are fueled directly by ammonia, a carbon-neutral fuel stored in the liquid state under low pressure. Liquid ammonia has advantages over compressed hydrogen gas, including higher energy density and facilitated distribution and refill. The beginning-of-life performance reported until recently for low-temperature DAFCs has been substantially lower than that of polymer electrolyte fuel cells fueled by hydrogen. We discuss here promising recent advances in electrocatalyst development, cell performance, and cell performance stability for low-temperature DAFCs, including beginning-of-life peak power density of 420 mW/cm², and operation over several days at constant current. In addition, we describe technology gaps that must be closed for low-temperature DAFCs to achieve the performance required for practical applications.