Gas Hydrate Formation in Reversed Micelles

We describe a technique to modify protein solubility and optimize enzyme activity in reversed micellar solutions. The technique is based on the ability of hydrates of natural gas to form in the micro-aqueous phase. Clathrate hydrates are crystalline inclusions of water and gas, and their formation in bulk water has traditionally been studied with relevance to natural gas recovery. We have found that hydrates can form in the environment of the microaqueous pools of reversed micelles, and that their extent of formation can be well controlled through the thermodynamic variables of temperature and pressure. Additionally, formation of hydrates affects the size and aggregation number of the micelles, and thus influences the solubility and conformation of encapsulated proteins. We demonstrate how the concept can be used in two applications: (i) protein extraction into reversed micelles and subsequent recovery, and (ii) optimization of enzyme activity in reversed micelles.     

Synthesis and Characterization of Metabolites and Potential Impurities of the Antiulcerative Drug Tenatoprazole

Tenatoprazole (Ulsacare^®) is a recently developed antiulcerative drug used for the treatment of both erosive and nonerosive gastroesophageal reflux disease. During the bulk synthesis of tenatoprazole, we have observed four impurities (tenatoprazole N‐oxide, tenatoprazole sulfone N‐oxide, N‐methyl tenatoprazole, and desmethoxy tenatoprazole) and two metabolites (tenatoprazole sulfide and tenatoprazole sulfone). The present work describes the synthesis and characterization of these impurities.     

A Novel Green Synthesis of Silver Nanoparticles Using Gum Karaya: Characterization,Antimicrobial and Catalytic Activity Studies

Stable silver nanoparticles have been synthesized using gum karaya acting as both reducing and stabilizing agent without using any synthetic reagent. The reaction is performed using water, which is an environmentally safe solvent. This reaction was carried out in an autoclave at a pressure of 15 psi and 120 °C temperature by varying the time. The influence of different parameters such as time, change of concentration of silver nitrate and concentration of gum karaya on the formation of silver nanoparticles has been studied. The synthesized silver nanoparticles are characterized by UV–Vis spectroscopy, FTIR, XRD and TEM. UV–Vis analysis of the sample confirmed the formation of silver nanoparticles exhibiting a sharp peak at a wavelength of 420 nm. TEM micrographs showed the formation of well-dispersed silver nanoparticles of size 2–4 nm. The antimicrobial activity of silver nanoparticles stabilized in gum karaya is tested against Escherichia coli, Micrococcus luteus and is found to be possessing inhibiting property. The silver nanoparticles stabilized in gum karaya exhibited very good catalytic activity and the kinetics of the reaction was found to be pseudo first order with respect to the 4-nitrophenol.     

Machine-Driven Chemoenzymatic Synthesis of Glycopeptide

Historically, researchers have put considerable effort into developing automation systems to prepare natural biopolymers such as peptides and oligonucleotides. The availability of such mature systems has significantly advanced the development of natural science. Over the past twenty years, breakthroughs in automated synthesis of oligosaccharides have also been achieved. A machine-driven platform for glycopeptide synthesis by a reconstructed peptide synthesizer is described. The designed platform is based on the use of an amine-functionalized silica resin to facilitate the chemical synthesis of peptides in organic solvent as well as the enzymatic synthesis of glycan epitopes in the aqueous phase in a single reaction vessel. Both syntheses were performed by a peptide synthesizer in a semiautomated manner.     

Asymmetric synthesis of (4S,5S)-2-oxo-4-phenyloxazolidine-5-carboxylic acid using a 1,2-addition of PhMgBr to an N-sulfinimine derived from (R)-glyceraldehyde acetonide and (S)-t-BSA

We report an asymmetric synthesis of (4S,5S)-2-oxo-4-phenyloxazolidine-5-carboxylic acid via stereoselective addition of phenylmagnesium bromide (PhMgBr) to an N-sulfinimine derived from (R)-glyceraldehyde acetonide. (S)- and (R)-Glyceraldehyde acetonides, important chiral synthons in synthetic organic chemistry, are prepared from the corresponding epichlorohydrin using an identical synthetic methodology.     

DMAP-catalyzed synthesis of 2-oxazolidinones from corresponding halohydrins using KOCN/DMF

We report facile and simple synthesis of a variety of 2-oxazolidinones from the corresponding halohydrins by reaction with KOCN in DMF catalyzed by DMAP. DMAP and temperature play key roles in enriching the yield of 2-oxazolidinones. A few examples in this Letter are applicable to pharmaceutically important processes.     

Catalytic Reduction of p‐Nitrophenol and Hexacyanoferrate (III) by Borohydride Using Green Synthesized Gold Nanoparticles

A simple and green approach for the synthesis of well‐stabilized gold nanoparticles (AuNPs) using gum Acacia (GA) is presented here. The gum acacia acts as the reductant and stabilizer. The synthesized gold nanoparticles were characterized by using ultraviolet visible (UV‐Vis), fourier transform infrared spectroscopy (FTIR), x‐ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. The UV‐Vis study revealed a distinct surface plasmon resonance at 520 – 550 nm, due to the formation of AuNPs. FTIR analysis showed the evidence that –OH groups present in the gum matrix were responsible in reducing the tetra chloroauric acid into AuNPs. XRD studies confirmed the formation of well crystalline nanoparticles with fcc structure and the particle size ranges from 4 – 29 nm, as indicated by TEM analysis. The synthesized gold nanoparticles exhibited homogeneous catalytic activity. The two model reactions studied were the reduction of p‐nitro phenol and the reduction of hexacyanoferrate (III) by borohydride ions. Both the reactions were monitored by UV‐Vis spectroscopy. The kinetic investigations were carried out for the AuNPs‐catalyzed reactions at different temperatures and different amount of catalyst.     

Cu(OTf)2/Cu-catalyzed four-component reaction: a facile synthesis of α-alkoxytriazoles via click chemistry

Aldehyde, alcohol, azide, and alkyne undergo smooth coupling by means of acetal formation, azidation, and a subsequent ‘click reaction’ in the presence of copper(II) triflate and copper metal in acetonitrile to furnish α-alkoxy-1,2,3-triazoles in good yields. The method provides a convenient route to prepare a wide range of triazoles in a one-pot operation via a four-component reaction.     

A facile synthesis of melatonergic antidepressant agomelatine

Agomelatine was synthesized from 8-aminonaphthalen-2-ol by diazotization-iodination, formylation, C–C bond formation by nitroaldol and Pd/C hydrogenation of β-nitrovinylnaphthalene followed by N-acetylation. The route reported employs readily and commercially viable starting materials and reagents, and can potentially be utilized for process synthesis of agomelatine.