A two-directional synthesis of (+/-)-perhydrohistrionicotoxin

An entirely two-directional synthesis of (+/-)-perhydrohistrionicotoxin is presented, utilizing a tandem oxime formation/Michael addition/[3 + 2] cycloaddition as the key step. This approach also constitutes formal syntheses of (+/-)-histrionicotoxin and (+/-)-histrionicotoxin 235A.     

A Review on Optimization Production and Upgrading Biogas Through CO2 Removal Using Various Techniques

Biogas from anaerobic digestion of organic materials is a renewable energy resource that consists mainly of CH₄ and CO₂. Trace components that are often present in biogas are water vapor, hydrogen sulfide, siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide, and nitrogen. Considering the biogas is a clean and renewable form of energy that could well substitute the conventional source of energy (fossil fuels), the optimization of this type of energy becomes substantial. Various optimization techniques in biogas production process had been developed, including pretreatment, biotechnological approaches, co-digestion as well as the use of serial digester. For some application, the certain purity degree of biogas is needed. The presence of CO₂ and other trace components in biogas could affect engine performance adversely. Reducing CO₂ content will significantly upgrade the quality of biogas and enhancing the calorific value. Upgrading is generally performed in order to meet the standards for use as vehicle fuel or for injection in the natural gas grid. Different methods for biogas upgrading are used. They differ in functioning, the necessary quality conditions of the incoming gas, and the efficiency. Biogas can be purified from CO₂ using pressure swing adsorption, membrane separation, physical or chemical CO₂ absorption. This paper reviews the various techniques, which could be used to optimize the biogas production as well as to upgrade the biogas quality.     

Fluence Rate Determines PDT Efficiency in Breast Cancer Cells Displaying Different GSH Levels

Photodynamic therapy (PDT) appears as a promising alternative in the treatment of breast cancer since it can be highly effective in curing cancer while preserving normal tissue. However, predicting outcomes in PDT still constitutes a great challenge. One of the parameters that are usually empirically determined is the rate of photon flux delivered to the tissue (light fluence rate). In the present study, we intended to understand why monolayers of human cells derived from mammary adenocarcinomas (MDA-MB-231 and MCF-7) respond quite differently to fluence rates (cells were irradiated either for 6 or for 16 min) at a fixed light dose (4.5 J cm⁻²) delivered with an array of LEDs in a typical methylene blue PDT protocol. While death rates of MDA-MB-231 cells were insensitive to the fluence rate, MCF-7 cells showed a quite impressive (three times) decrease in cell death levels in the shorter irradiation protocol. Independent on cell type cell death was invariably correlated with the depletion of reduced glutathione intracellular levels and consequently with widespread redox misbalance. Our data show the potential to optimize fluence rates to provide exhaustion of the cell antioxidant responses in order to circumvent therapy resistance of breast tumors.     

Direct synthesis of aliphatic vinyl aziridines

The synthesis of vinyl aziridines, by the reactions of a range of diphenylphosphinyl and p-toluenesulfonyl alkyl aldimines with the ylide derived from S-allyl tetrahydrothiophenium bromide, are reported.     

Combining two-directional synthesis and tandem reactions. Part 4: A concise approach to the spirocyclic core of halichlorine and the pinnaic acids

A synthesis of the spirocyclic core structure of halichlorine, an inhibitor of the induced expression of VCAM-1 and the pinnaic acids, inhibitors of PLA₂, is presented. A two-directional strategy is employed, in conjunction with a tandem oxime formation/Michael addition/cycloaddition to form the key azaspirocyclic skeleton in a very direct manner.