Synthesis of an aryl 2-deoxy-β-glycosyl tetrasaccharide to probe retaining endo-glycosidase mechanism

The synthesis of the 1,3–1,4-β-glucanase substrate analogue 4-nitrophenyl O-β-d-glucopyranosyl-(1→4)-O-β-d-glucopyranosyl-(1→4)-O-β-d-glucopyranosyl-(1→3)-2-desoxi-β-d-glucopyranoside 2 is reported. Starting from the main tetrasaccharide obtained by enzymatic depolymerization of barley β-glucan, the synthetic scheme involves preparation of the corresponding 3-O-substituted glycal which was converted into a 2-deoxy-α-glycosyl iodide as a glycosyl donor. The key glycosylation step was successfully achieved by nucleophilic substitution of the iodide donor with 4-nitrophenolate with high β-selectivity.     

Hydrogen-bonded self-assemblies in a polychlorotriphenylmethyl radical derivative substituted with six meta-carboxylic acid groups

The synthesis, self assembly and magnetic properties of a polychlorotriphenylmethyl radical, substituted with six meta-carboxylic groups, are reported showing that radical-radical hydrogen bonds in the solid state yield to very weak intermolecular ferromagnetic interactions.     

Multistability in a BEDT-TTF based molecular conductor

The low dimensional organic conductor (BEDT-TTF)(2)Br(1.3)I(1.1)Cl(0.6) [BEDT-TTF = bis(ethylenedithio)tertathiafulvalene] is shown to be a unique molecular solid that exists in three crystalline polymorphic forms (alpha'-, alpha' "-, beta' '-phase) and, surprisingly, is able to adopt the same metal-like beta' '-phase at both low (T < 185 K) and high (T > 395 K) temperatures. Several crystals of the alpha'- and alpha' "-phases have been studied using three different techniques: dc-conductivity measurements, ESR spectroscopy, and X-ray diffraction analysis. All these techniques show the existence of the reversible semiconductor <--> metal (alpha' " <--> beta' ') phase transition at both high and low temperatures as well as the alpha' <--> alpha' " phase transition at high temperatures. The phase transitions of these polymorphs are characterized by huge hysteresis and dramatic changes in the transport and magnetic properties. Based on ab initio calculations, it is suggested that dipole-dipole interactions can play a key role in the rich polymorphism of this molecular solid.     

A robust nanocontainer based on a pure organic free radical

A new pure organic paramagnetic porous molecular material, which combines hydrophilic windows with large hydrophobic nanocontainers, is shown to be stable even in absence of solvent guest molecules.     

Plasma Nitrogen Oxides Synthesis in a Milli-Scale Gliding Arc Reactor: Investigating the Electrical and Process Parameters

Nitrogen fixed in the form of nitrogen oxides is essential to produce fertilizers and many other chemical products, which is vital to sustain life. The performance of a milli-scale gliding arc reactor operated under atmospheric pressure has been studied for nitrogen oxides synthesis. In this work, the electrical and process parameters of the gliding arc reactor, such as frequency, pulse width, amplitude and feed ratio were investigated respectively. The experiments were performed at 1 L/min in a gliding arc discharge regime. The highest concentration of NO_x was found to be ~1 % at energy consumption of 10 kWh/kg of NO_x. Increase in frequency, pulse width and amplitude resulted in an increased specific energy input and NO_x concentration. The feed ratio (N₂/O₂) affected the amount of NO and NO₂ produced, which gives possibility to independently obtain the desired ratio of NO/NO₂ by tuning the electrical and process parameters.     

Hydrolysis of Hydrophobic Esters in a Bicontinuous Microemulsion Catalysed by Lipase B from Candida antarctica

Selective enzyme‐catalysed biotransformations offer great potential in organic chemistry. However, special requirements are needed to achieve optimum enzyme activity and stability. A bicontinuous microemulsion is proposed as reaction medium because of its large connected interface between oil and water domains at which a lipase can adsorb and convert substrates in the oil phase of the microemulsion. Herein, a microemulsion consisting of buffer–n‐octane–nonionic surfactant C_iE_j was used to investigate the key factors that determine hydrolyses of p‐nitrophenyl esters catalysed by the lipase B from Candida antarctica (CalB). The highest CalB activity was found around 44 °C in the absence of NaCl and substrates with larger alkyl chains were better hydrolysed than their short‐chained homologues. The CalB activity was determined using two different co‐surfactants, namely the phospholipid 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) and the sugar surfactant decyl β‐D ‐glucopyranoside (β‐C₁₀G₁). The results show the CalB activity as linear function of both enzyme and substrate concentration with an enhanced activity when the sugar surfactant is used as co‐surfactant.