Current Organic Chemistry - Volume 20, Issue 19, 2016

As one of the main greenhouse gases and a kind of important "potential carbon resources", CO2 has received people's widespread attention. The CO2 separation can be achieved via conventional methods, such as pressure swing adsorption, dry and wet amine scrubbing, and cryogenic distillation etc. However, all these methods will require high cost. The membrane technology could offer the opportunity to meet the demand for high energy efficiency, lower cost, and operation simplicity for gas separation. It has been found that the polymer membranes containing CO2-favored organic units show outstanding CO2 separation performance due to the unique affinity between CO2 and the units. Thus, it is highly important to extensively explore novel CO2-favored organic units and investigate the effects of CO2-favored organic units on gas separation. In this review, the CO2-favored organic units recently utilized for fabricating CO2 separation membranes have been reviewed. The development of the CO2- favored organic units in CO2 separation membranes in the future has also been prospected.

Cyclic imides are commonly encountered structural motifs in natural and synthetic molecules with remarkable pharmacological properties. They are also used widely for further functionalization through various chemical transformations. Currently, renewed focus has been devoted worldwide on this important class of compounds for their potential new applications especially in the area of medicinal / pharmaceutical chemistry as well as in drug discovery. Consequently, their syntheses have attracted considerable interest. Various innovative methodologies have recently been developed in order to access and functionalize this class of compounds. For example, the combination of classical as well as modern reactions allowed synthetic chemists to perform the straight forward and direct synthesis of diversity based library of compounds, often in 1-2 steps. The present report will cover the relevant and recent advances in the field of occurrences, synthesis and chemical reactions of cyclic imides mainly from 1980 to the end of 2015.

The marine environment is considered as a precious source of novel marinederived natural products which offer valuable, safer and affordable promising compounds. Various universities and pharmaceutical industries are more and more interested in these novel compounds due to their exceptional health benefits. Unique ingredients found in the marine biosphere are polysaccharides, polyphenols, polyunsaturated fatty acids (PUFA), enzymes and bioactive peptides, minerals and vitamins to name a few. In order, to exploit sustainably the treasures of the ocean, in depth understanding and research are a must to pave the way for a better future. This review focuses mainly on the structure, biological properties and applications of some polysaccharides derived from marine macroalgae, marine fauna as well as exopolysaccharides (EPS) from marine microorganisms.

Nanocatalysis as an immerging research topic has attracted much attention in the past years. Functionalized materials with a nano-/submicro-dimension displayed a more significant and dramatically powerful catalytic capability than traditional catalysts in organic chemical reactions due to the increased surface area and multiple catalytic centers. Especially, for chiral catalysis and natural product synthesis, nanocatalysts are and will play an important role in enhancing the yield and TON (turn-over number), facilitating the purification and realizing the efficient catalyzation in a recycling manner. This review article aims to conclude the recent proceedings on nanocatalysis, such as catalyst design, construction and modifications, and their applications in organic reactions, particularly to chemo-selective and coupling reactions. Further discussions will outlook the future trends as well as current challenges in this field.

A new generation of natural phosphate-supported palladium was synthesized by treating natural phosphate with bis(benzonitrile)palladium(II) chloride in acetone. Its catalytic activity was evaluated in selective hydration of nitriles. The reactions proceeded in the presence of 0.4 mol% of the palladium catalyst at 160°C in water under microwave irradiation. Several nitriles, including aromatic and heteroaromatic nitriles, were converted to corresponding amides in good yields under neutral conditions. The recyclability and low cost availability of this solid support make this approach very attractive. It encourages new fields of research in the valorization of this natural resource and can change the current view of heterogeneous catalysis.

Ochratoxin A (OTA) is a mycotoxin whose dangers have been sufficient for many countries to regulate its presence in various foods. In Mediterranean countries, the black Aspergilli group, in particular Aspergillus carbonarius causes the highest OTA contamination in fruit. Here, we describe the synthesis of three novel styryl heterocyclic compounds and their effect on (1) the prevention of OTA biosynthesis by A. carbonarius cultured in a conducive liquid medium, (2) Reactive Oxygen Species (ROS) formation, and (3) lipoxygenase (LOX) activity. The most effective control of OTA biosynthesis was achieved with (E)-3-(3,4-dimethoxy-styryl)-thiophene. In fungal cultures treated with this compound at 5, 25, 50, and 100 ppm, OTA biosynthesis decreased by 45% to 95% until the experiment's conclusion (8 days). (E)-3-(3-methoxy-4-acetoxy-styryl)-thiophene significantly inhibited OTA biosynthesis (about 50%). However, this effect lasted for only few days when used at 5 or 25 ppm and up to 8 days when used at 50 or 100 ppm; (E)-3-(3-methoxy-4-hydroxy-styryl)-thiophene did not exert any control on OTA biosynthesis. The same compounds also were assayed for their ability to affect LOX activity and ROS formation. The compounds able to control OTA biosynthesis also significantly inhibited ROS formation and LOX activity. The nature of the substituent in para position strongly affects the molecule’s reactivity. Lower reactivity enhances the inhibition of OTA biosynthesis, in particular long-term. Natural compounds present in edible plants having a styryl heterocyclic scaffold may be effective inhibitors of OTA biosynthesis.