Non-phospholipid liposomes with high sterol content display a very limited permeability

We demonstrate that it is possible to form non-phospholipid fluid bilayers in aqueous milieu with a mixture of palmitic acid (PA),cholesterol (Chol),and cholesterol sulfate (Schol) in a molar proportion of 30/28/42.These self-assemblies are shown to be bilayers in the liquid ordered phase.They are stable between pH 5 and 9.Over this pH range,the protonation/deprotonation of PA carboxylic group is observed but this change does not appear to alter the stability of these bilayers,a behavior contrasting with that observed for binary mixtures of PA/Chol,and PA/Schol.The multilamellar dispersions formed spontaneously from the PA/Chol/Schol mixture could be successfully extruded to form Large Unilamellar Vesicles (LUVs).These LUVs show interesting permeability properties,linked with their high sterol content.These non-phospholipid liposomes can sustain a pH gradient (pH internal 8/pH external 6) 100 times longer than LUVs made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol,with a molar ratio of 60/40.Moreover,the non-phospholipid LUVs are shown to protect ascorbic acid from an oxidizing environment (1 mM iron(III)).Once entrapped in liposomes,ascorbic acid displays a degradation rate similar to that obtained in the absence of iron(III).These results show the possibility to form novel nanocontainers from a mixture of a monoalkylated amphiphile and sterols,with a good pH stability and showing interesting permeability properties.     

Voltammetry coupled to mass spectrometry in the presence of isotope O labeled water for the prediction of oxidative transformation pathways of activated aromatic ethers: Acebutolol

The coupling between an electrochemical cell (EC) and a mass spectrometer (MS) is a useful screening tool (EC-MS) to study the oxidative transformation pathways of various electroactive species. For that purpose, we showed that the EC-MS method, carried out in the presence and absence of isotope ¹⁸O labeled water leads not only to a fast identification of oxidation products but also leads to a fast elucidation of the mechanism pathway reaction. We examined herein the case of the electrochemical hydrolysis of activated aromatic ether. Acebutolol (β-blockers) was selected herein as model of activated aromatic ether, and its electrochemical oxidation was examined in both the presence and absence of isotope ¹⁸O labeled water. To elucidate electrochemical hydrolysis pathway reaction: O-dealkylation or O-dealkoxylation, our approach was used to prove its applicability. The electrochemical oxidation mechanism was then elucidated showing an O-dealkoxylation reaction. In addition, density functional theory (DFT) calculations fully support the experimental conclusions.     

Synthesis of Anhydronectriachrysone,an Extensively Conjugated γ-Pyrone

The synthesis of anhydronectriachrysone (2) through the DIBAH reduction of toralactone (3), followed by dehydration of the corresponding lactol (4) is reported (38% yield).     

A Convenient Laboratory Preparation of N,N-Dimethyl-dichloro-methylene-iminium Chloride (Phosgene-iminium chloride)

A method of preparation of the title compound 1a avoiding the use of gaseous chlorine is described. Tetramethylthiuram disulfide 4 is oxidized with sulfuryl chloride to dime thyl thiocarbamoyl chloride 5, which is converted to 1a by means of phosphorus pentachloride.     

Preparation of the N-(2-Bromo-2-Nitroethenyl) Benzenamine: The First One-Pot Synthesis of a β-Halo-β-Nitroenamine

Bromonitromethane, triethyl orthoformate and aniline react together, in a one-flask procedure, to afford the title compound.     

How to broaden the light reflection band in cholesteric liquid crystals? A new approach based on polymorphism

Cholesteric liquid crystals (CLCs) may selectively reflect light when the helicoidal pitch is of the order of the wavelength of the incident beam propagating along the helix axis. The reflection bandwidth is dependent on the birefringence and is limited to a few tens of nanometers, which is insufficient for applications such as white-on-black reflective displays. Recent studies have shown that CLC polymer networks with a pitch gradient induce a broadening of the reflection bandwidth over several hundreds of nanometers. Most related processes rely on photocrosslinking reactions with a UV-gradient in a mixture made of chiral and achiral monomers with different UV-reactivities. Here a new experimental route exploiting the polymorphism of the mixture is presented. The basic concept lies in a thermally-induced pitch variation simultaneously carried out with the UV-crosslinking reaction. The optical behaviour is investigated in parallel with the cross-sectional microstructure as observed by transmission electron microscopy.     

Derivatives of 3-Deoxy-3-(N-Hydroxyamino)-D-Ribose

Abstract

A series of 3-(N-arylmethyl-N-hydroxyamino)-l,2-O-cyclopentylidene-3-deoxy-5-O-toluoyl-α-D-riboses has been prepared. The blocking groups used were chosen to allow an easy nucleosidation of these compounds to spin labelled analogs of natural nucleosides. The conformational behavior of the N-arylmethyl-N-hydroxyamino group has been studied using ³/_CH NMR coupling data and molecular mechanics computations. Upon spontaneous oxidation, these hydroxylamines led to the corresponding aminoxyl free radicals which were submitted to EPR spectroscopy and quantum mechanical computations at a semiempirical level (PM3).     

From Pyranosuloses and Pyranosenuloses to Deoxy Hydroxyamino Sugars

Abstract

Deoxy hydroxyamino sugars represent a potentially useful series of sugar analogs owing mainly to the fact that they oxidize spontaneously to nitroxide free radicals to give spin-labeled sugar derivatives whose structure is very close to that of the parent sugar.₃ We describe herin two synthetic pathways towards these compounds, reduction of sugar oximes and conjugate addition to enolones derivatives, both in the pyranose series.