Transformation of Pectins into Non-Ionic or Anionic Surfactants Using a One-Pot and Cascade Mode Process.

The present article describes the one-pot synthesis of double- and single-tailed surfactants by a cascade process that involves the hydrolysis/butanolysis of pectins into butyl galacturonate monosaccharides followed by transesterification/transacetalisation processes with fatty alcohols, and subsequent aqueous basic and acid treatments. The cascade mode allows the depolymerisation to proceed more efficiently, and the purification conditions are optimised to make the production of single-tailed surfactants more manufacturable. These products in a pure form or as mixtures with alkyl glycosides resulting from butanolysis and transglycosylation of pectin-derived hexoses, exhibit attractive surface-tension properties, especially for the -oleyl ᴅ-galactosiduronic acid products.

Thermotropic liquid crystalline glycolipids.

Are the liquid crystalline properties of the materials of living systems important in biological structures, functions, diseases and treatments? There is a growing consciousness that the observed lyotropic, and often thermotropic liquid crystallinity, of many biological materials that possess key biological functionality might be more than curious coincidence. Rather, as the survival of living systems depends on the flexibility and reformability of structures, it seems more likely that it is the combination of softness and structure of the liquid-crystalline state that determines the functionality of biological materials. The richest sources of liquid crystals derived from living systems are found in cell membranes, of these glycolipids are a particularly important class of components.

First o-glycosylation from unprotected 1-thioimidoyl hexofuranosides assisted by divalent cations.

The preparation of O-hexofuranosides was accomplished from unprotected 1-thioimidoyl furanosides as donors. The present methodology was first used for the synthesis of octyl galactofuranoside and further extended to D-galactofuranose-containing disaccharides. Within this study, we emphasized the need for additional complexing cations to maintain the furanose ring in its initial size.

Recent progress in the field of beta-(1,3)-glucans and new applications.

Beta-(1,3)-glucans are widely distributed within microorganisms or seaweeds in which they act as membrane components or for energy storage, respectively. Since these glucans are not biosynthesized by mammals, they are likely to activate the immune system of their host. Since the discovery of their positive involvement as immunomodulator agents, numerous studies were published all around the glycosciences.

Synthesis of galactofuranose-containing disaccharides using thioimidoyl-type donors.

Four galactofuranose-containing disaccharides have been prepared utilising various thioimidates [Galf-SC(NR)XR'] and suitably protected acceptors as key precursors. We observed that the efficiency of the coupling reactions was particularly dependent on the aglycon present on the furanosyl donor when copper(II) ions were used as the promoter, and that activation could be correlated with the nature of the third heteroatom, X.

Monolayer lipid membrane-forming dissymmetrical bolaamphiphiles derived from alginate oligosaccharides.

New dissymmetrical neutral-cationic or anionic-cationic alpha,omega-diamido bolaamphiphiles have been synthesized in which the polar headgroups are derived from alginate and glycine betaine and which exhibit monolayer lipid membrane vesicles, large lamellae and rods.

Archaeosomes based on novel synthetic tetraether-type lipids for the development of oral delivery systems.

The in vitro stability of archaeosomes made from novel synthetic membrane-spanning tetraether lipids was evaluated in conditions mimicking those of oral route application in terms of bile salts, serum and low pH..

General one-step synthesis of free hexofuranosyl 1-phosphates using unprotected 1-thioimidoyl hexofuranosides.

A general one-step strategy is developed for the synthesis of hexofuranosyl 1-phosphates starting from new unprotected glycofuranosyl donors. It required first the preparation of new 1-thiohexofuranosides bearing a thioimidoyl heterocycle as a leaving group. The presence of sulfur and/or nitrogen atom(s) on the aglycon allowed remote activation of these thioglycofuranosides by anhydrous phosphoric acid and led to the target phosphates 9, 27, 29, and 30 in good to excellent selectivities and, more importantly, with very limited or no ring expansion.

Glucan-like synthetic oligosaccharides: iterative synthesis of linear oligo-beta-(1,3)-glucans and immunostimulatory effects.

Small reducing and linear oligo-beta-(1,3)-glucans, which are able to act as phytoallexin elicitors or as immunostimulating agents in anticancer therapy, were synthesized according to an iterative strategy that involved a unique key monosaccharidic donor. To avoid anomeric mixtures, the reducing entity of the target oligomers was first locked with benzyl alcohol and further selective deprotection of the 3-OH with DDQ afforded the desired building block as an acceptor. The latter was then used in a second cycle of glycosylation/deprotection to afford the desired disaccharide, and successive reiterations of this process provided the desired oligomers.

Synthesis and supramolecular assemblies of bipolar archaeal glycolipid analogues containing a cis-1,3-disubstituted cyclopentane ring.

Unsymmetrical archaeal tetraether glycolipid analogues 1-2 incorporating a 1,3-disubstituted cyclopentane ring into the bridging chain have been synthesized. The cyclopentane has been introduced with a totally controlled cis configuration, either into the middle of the aliphatic chain or at three methylene groups from the glycerol unit linked to the bulkier disaccharide residue. Freeze-fracture and cryotransmission electron microscopy experiments clearly demonstrated unprecedented glycolipid supramolecular organizations involving two-by-two monolayer associations coupled with interconnection and fusion phenomena.

Efficient gene transfer into human epithelial cell lines using glycosylated cationic carriers and neutral glycosylated co-lipids.

To date, no clear and constant relationship has been established between the chemical structure and the efficiency of non-viral transfection reagents. Despite the improvement of synthetic transfection systems, the capacity to transfect a target cell in a specific way is still a major challenge that gene therapy needs to overcome to be successful. Consequently, we developed a strategy aimed specifically at improving transfection of targeted human epithelial cells and to examine the possible effects of electrostatic interactions.

A new synthesis of the oligosaccharide domain of acarbose.

Synthesis of the oligosaccharide domain of acarbose was reinvestigated and was optimally performed using a maltosidic acceptor, already bearing a alpha-D-Glc-(1-->4)-D-Glc bond, and a new D-fucopyranosyl donor. The crucial glycosylation step was improved by varying three different parameters and notably by focusing on the C-4 protecting group of the fucosyl residue, solvent and promoter. The resulting trisaccharide was further transformed into an electrophilic species in order to open further derivatization perspectives for designing new acarbose analogues.

Beta-anomeric selectivity in the glycosidation of D-mannofuranurono-6,3-lactone catalyzed by boron trifluoride diethyl etherate.

The BF3-promoted glycosylation of D-mannofuranurono-6,3-lactone with dodecanol or methanol afforded n-alkyl beta-D-mannofuranosidurono-6,3-lactone. Reduction of n-dodecyl beta-D-mannofuranosidurono-6,3-lactone with sodium borohydride yielded the corresponding alkyl beta-D-mannofuranoside.

A novel synthesis of D-galactofuranosyl, D-glucofuranosyl and D-mannofuranosyl 1-phosphates based on remote activation of new and free hexofuranosyl donors.

The selective synthesis of 1,2-cis-hexofuranosyl 1-phosphates was readily accomplished according to a procedure based on the 'Remote Activation Concept'. This approach required (i) the preparation of suitable 1,2-trans-hexofuranosyl donors, so that new heterocyclic thiofuranosides were designed and synthesized, (ii) the stereocontrolled phosphorylation of the corresponding unprotected donors and (iii) the simple and fast purification of the resulting anomeric phosphates. This approach showed to be equally efficient in the galactose, glucose and mannose series.

Epoxidation of allylic alcohols in aqueous solutions of non surfactant amphiphilic sugars.

A variety of cyclic and acyclic allylic alcohols undergo efficient chemo-, regio- and/or stereoselective epoxidations in neutral aqueous solutions of amphiphilic carbohydrates (sucrose, L-arabinose, methyl or ethyl beta-D-fructopyranoside) by using dilute hydrogen peroxide in the presence of molybdic or tungstic salts.

Cationic lipids derived from glycine betaine promote efficient and non-toxic gene transfection in cultured hepatocytes.

Background: The low efficiency and toxicity of transfection in a primary culture of hepatocytes using cationic lipids remains a limiting step to the study of gene function and the setting up of non-viral gene therapy.

Methods: A novel class of cationic lipids (GBs) derived from natural glycine betaine compounds covalently linked to acyl chains by enzymatically hydrolysable peptide and ester bonds, a structure designed to reduce cytotoxicity, was used to improve transfection efficiency in a primary culture of rat hepatocytes. The relationship between lipid structure, lipoplex formulation and transfection efficiency was studied using six GBs (12-14-16, 22-24-26) varying in their spacer and acyl chains.

Transient transmission of a transgene in mouse offspring following in vivo transfection of male germ cells.

Sperm-mediated gene transfer in vertebrates has undergone various developments over the last few years, in different laboratories. In the present study, we microinjected a circular plasmid, carrying the lacZ reporter gene mixed with noncommercial cationic lipids, into the seminiferous tubules of anesthetized adult mice. Histochemical analysis was used to estimate the transfection efficiency 48-96 hr and 40 days after injection.

Supramolecular self-assembling properties of membrane-spanning archaeal tetraether glycolipid analogues.

The self-assembling properties of a new series of archaeal tetraether glycolipid analogues 1-6 that are characterized by a bipolar architecture with two similar or different glycosidic and/or phosphate polar heads and a lipid core possessing a cyclopentane unit and/or branched chains were studied by means of differential scanning calorimetry, optical microscopy, X-ray scattering, freeze-fracture electron microscopy and dynamic light scattering. Unsymmetrical phosphate derivatives 1 and 2 spontaneously formed thermostable multilamellar and unilamellar vesicles in which most of the bipolar lipids adopted a trans-membrane conformation, as revealed by freeze-fracture electron microscopy. Supramolecular aggregates of neutral glycolipids 3-6 were found to depend on both the saccharidic polar heads and the chain composition.

Synthetic Approaches to Novel Archaeal Tetraether Glycolipid Analogues.

Symmetrical and unsymmetrical archaeal tetraether glycolipid analogues have been prepared. The syntheses are based upon the elaboration of lipid cores from versatile chiral starting materials followed by simultaneous or sequential introduction of polar headgroups. Three pathways (A-C) were elaborated for the synthesis of stereochemically defined lipids 14-16 characterized by a straight bridging spacer and two dihydrocitronellyl chains attached to glycerol units at the sn-3 and sn-2 positions, respectively.

Liquid chromatography of polyglycerol fatty esters and fatty ethers on porous graphitic carbon and octadecyl silica by using evaporative light scattering detection and mass spectrometry.

A liquid chromatographic method has been developed for the analysis of polyglycerol fatty esters and fatty ethers which are non-ionic surfactants. Two methods were compared using either octadecyl silica or porous graphitic carbon. The octadecyl silica system with a hydroorganic mobile phase enables to compare the hydrophobic behavior of the compounds.

New biocompatible cationic amphiphiles derivative from glycine betaine: a novel family of efficient nonviral gene transfer agents.

With the aim of developing new efficient agents for transfecting of eukaryotic cells we have designed and synthesized a novel family of cationic lipid vectors derived from glycine betaine. In this study we present three novel molecules differing by the length of their aliphatic chains (R=12,R=14,R=16). The lyotropic properties of these cationic lipids have been determined, and their transfection efficiency on different cell lines evaluated, using a luminescent assay.

Self-Organization and Formation of Liquid Crystal Phases by Molecular Templates Related to Membrane Components of Archaebacteria.

Tubular supramolecular aggregates are formed from glycolipids 1, which are closely related to natural components of membranes of archaebacteria. The glycolipids exhibit disordered columnar thermotropic and hexagonal lyotropic liquid crystal phases. Whereas formation of the mesophases is insensitive to stereochemical factors, formation of the tubules is dependent on the configuration of the stereocenters that are shown in the picture but not specified.

Adsorption of Glycosidic Surfactants at the Mercury Electrode.

The adsorption of glycosidic surfactants from aqueous electrolyte solutions on a mercury electrode was studied by means of differential capacitive measurements (tensammetric method). The adsorption behavior of the mono- and disaccharidic surfactants studied is discussed in relation to their micellar properties, in particular their respective critical micellar concentration (CMC). With monosaccharidic surfactants, a broad and bell-shaped peak is observed on the tensammetric curves and it suggests the formation of a monolayer called hemimicelle at the mercury electrode.

Brominated detergents as tools to study protein-detergent interactions.

In order to study protein-detergent short-range interactions, we analyzed the quenching by brominated detergents of reticulum sarcoplasmic (SR) Ca(2+)-ATPase intrinsic fluorescence. For this purpose, 7,8-dibromododecyl beta-maltoside and 2-O-(10,11-dibromoundecanoyl)sucrose, brominated analogs of two non-ionic detergents, the frequently used dodecylmaltoside and the newly synthesized 2-O-lauroylsucrose respectively, were prepared. Rayleigh scattering measurements showed that the brominated detergents efficiently and rapidly solubilized SR vesicles like their non-brominated analogs although at slightly higher concentrations.

A new synthesis of 6-O-acylsucroses and of mixed 6,6'-di-O-acylsucroses.

Various 6-O-acylsucroses were synthesized in good yields from unprotected sucrose in N,N-dimethylformamide and the appropriate 3-acylthiazolidine-2-thiones 6 or 3-acyl-5-methyl-1,3,4-thiadiazole-2(3H)-thiones 7. A selective ionization of the free sugar by sodium hydride or triethylamine, followed by acylation with 6, gave 2-O-acylsucroses which were subjected in situ to intramolecular isomerizations using 1,8-diazabicyclo[5.4.