Current Organic Chemistry - Volume 19, Issue 13, 2015

Microorganisms produce a large number of peptide-based natural products that display a broad range of biologically interesting properties, including antimicrobial, immunosuppressant, and anticancer activities, as well as behaving as virulence factors and signaling molecules. These peptide natural products are composed of proteinogenic amino acids, as well as a number of other compound classes, including non-proteinogenic amino acids, aryl acids, fatty acids, hydroxyl acids, heterocyclic rings, and sugars, which provide a complex level of chemical diversity. Many of these natural products are biosynthesized by large, highly versatile multifunctional megasynthetases, which are known as nonribosomal peptide synthetases (NRPSs). The adenylation (A) domains found in all NRPS modules are essential catalytic components and function as gatekeepers to select the appropriate amino acid building blocks during nonribosomal peptide (NRP) biosynthesis. The results of extensive periods of genetic, biochemical, and bioinformatic investigations have provided a detailed understanding of the functional characteristics and molecular basis underpinning the A domain enzymology in NRP biosynthesis. This review will therefore focus on the recent discoveries and breakthroughs in the structural elucidation, molecular mechanism, and chemical biology underlying the A domains within NRPS enzymes.

The studies on the reaction of arynes with the π-bond are limited, although synthetic chemistry using aryne has attracted substantial attention. This review highlights the insertion of arynes into the π-bond giving the formal [2+2] cycloaddition-type adducts. In this review, the synthetic organic reactions involving the [2+2]-type reactions of arynes with the carbon-carbon double bond, the carbon-heteroatom double bond and the heteroatomheteroatom double bond are summarized.

The excellent advantages of cesium such as short reaction times, small amount of reagent used, high yields of the products, milder reaction conditions, and easy work-up procedures counter balanced its higher cost. From the last two decades, the use of cesium salts has received an increasing interest in numerous varieties of synthetic conversions. Today, the use of cesium salts has reached the industrial acceptance. For example, palladium catalyzed coupling reactions like the Suzuki coupling or the Buchwald amination reactions use the cesium salts. However, cesium salts are also utilized in direct nucleophilic substitution reactions since they have replaced the standard bases. This is the first review in this area which exclusively deals with recent developments in Cs salt promoted reactions with special focus on mechanistic aspects as well as on the recent applications in drug synthesis. Today, cesium carbonate (Cs2CO3), cesium fluoride (CsF), cesium acetate (CsOAc) and cesium hydroxide monohydrate (CsOH·H2O) are the most frequently used cesium compounds in the organic synthesis.

During the past few decades, polymer nanocomposites have gained momentum for designing materials that exhibit synergistic properties by overcoming the inherent limitations of pure materials particularly conducting polymers (CPs). Clays have been extensively employed as hosts for developing intercalated nanocomposites. The growth of conducting polymers in the interlayer region of the clays has shown to dramatically improve the properties of conducting polymers. This review highlights the latest developments in syntheses and characterization of conducting polymer intercalated clay nanocomposites. The classification of nanocomposites in this review is based on the utilization of various clays and their specific properties to design these conducting polymer intercalated nanocomposites.

In this paper we report a new strategy for the synthesis of isoindolo[2,1-b]isoquinolines. N-(1,2- Diphenylethyl)acetamides prepared from the corresponding deoxybenzoins were used as starting material. Double cascade cyclization of the amides promoted by oxalyl chloride and stannyl chloride afforded the oxidized isoindolo[ 2,1-b]isoquinolinone derivatives, which by reduction with a BH3·THF complex gave the 5,7,11b,12- tetrahydroisoindolo[2,1-b]isoquinolines 1b and 1d. Cyclization and reduction were also carried out in one-pot reaction improving the overall yield. DFT structural analysis of the tetrahydro derivatives showed a constrained and planar structure similar to that of camptothecin. SiO2 nanoparticles of 1b (1b-SiNP) were also prepared. This hybrid material provides a very good bioavailability for these compounds in aqueous systems.