Alkyl Glycosides Research Articles

Catalytic glycosylation of glucose with alkyl alcohols over sulfonated mesoporous carbons

Herein we investigated the catalytic performances of sulfonated mesoporous carbons in the glycosylation of carbohydrates with alkyl alcohols. Catalytic performances were compared to common solid acid catalysts previously reported for this reaction. Under optimized conditions, the targeted alkyl glycosides were obtained in 85% yield, together with a turn over frequency and a space time yield higher than those of the best heterogeneous catalysts reported so far in such reaction. Furthermore, the presence of mesoporous channels significantly lowered the deactivation rate of the catalyst in comparison to a non-porous sulfonated carbon.

Complex structures of MoeN5 with substrate analogues suggest sequential catalytic mechanism

The antibiotic moenomycin A is a phosphoglycerate derivative with a C25-moenocinyl chain and a branched oligosaccharide. Formation of the C25-chain is catalyzed by the enzyme MoeN5 with geranyl pyrophosphate (GPP) and the sugar-linked 2-Z,E-farnesyl-3-phosphoglycerate (FPG) as its substrates. Previous complex crystal structures with GPP and long-chain alkyl glycosides suggested that GPP binds to the S1 site in a similar way as in most other α-helical prenyltransferases (PTs), and FPG is likely to assume a bent conformation in the S2 site. However, two FPG derivatives synthesized in the current study were found in the S1 site rather than S2 in their complex crystal structures with MoeN5. Apparently S1 is the preferred site for prenyl-containing ligand, and S2 binding may proceed only after S1 is occupied. Thus, like most trans-type PTs, MoeN5 may employ a sequential ionization-condensation-elimination mechanism that involves a carbocation intermediate.

Hydrogenated Diglucose Detergents for Membrane-Protein Extraction and Stabilization.

We report herein the design and synthesis of a novel series of alkyl glycoside detergents consisting of a nonionic polar headgroup that comprises two glucose moieties in a branched arrangement (DG), onto which octane-, decane-, and dodecanethiols were grafted leading to ODG, DDG, and DDDG detergents, respectively. Micellization in aqueous solution was studied by isothermal titration calorimetry, 1H NMR spectroscopy, and surface tensiometry. Critical micellar concentration values were found to decrease by a factor of ∼10 for each pair of methylene groups added to the alkyl chain, ranging from ∼0.05 to 9 mM for DDDG and ODG, respectively. Dynamic light scattering and analytical ultracentrifugation sedimentation velocity experiments were used to investigate the size and composition of the micellar aggregates, showing that the aggregation number significantly increased from ∼40 for ODG to ∼80 for DDDG. All new compounds were able to solubilize membrane proteins (MPs) from bacterial membranes, insect cells, as well as the Madin-Darby canine kidney cells. In particular, native human adenosine receptor (A2AR) and bacterial transporter (BmrA) were solubilized efficiently. Striking thermostability improvements of +13 and +8 °C were observed when ODG and DDG were, respectively, applied to wild-type and full-length A2AR. Taken together, this novel detergent series shows promising detergent potency for solubilization and stabilization of membrane proteins (MPs) and thus makes a valuable addition to the chemical toolbox available for extracting and handling these important but challenging MP targets.

Synthesis and properties of sugar-based surfactants alkoxyethyl β-D-glucopyranoside

Alkyl glycosides as modern industrial manufactured products are important. Furthermore, the better water solubility should make them a greater potential application value. In this study, an improvement of water solubility has been realized by adding the oxyethene fragment (−OCH2CH2) as a hydrophilic spacer to the conventional alkyl glucoside structure, and the excellent surface properties of the alkyl glucoside were still maintained. The amphipathic properties of the prepared alkoxyethyl β-D-glucopyranoside can be adjusted by the alkyl chain length (n). Alkoxyethyl β-D-glucopyranosides were found to be water soluble with n ≤ 10. For both of CMC and γCMC, there was a monotonous decreasing trend with increasing the alkyl chain length. Such amphipathic molecules adsorbed preferentially on the solution surface and then formed spontaneously micelles in the aqueous solution by the hydrophobic effect. Nonyloxylethyl β-D-glucopyranoside exhibited the finest foaming property, as well as the strongest emulsifying capacities in the rapeseed oil/water system and the toluene/water system. In addition, alkoxylethyl β-D-glucopyranoside (n = 9–14) had thermotropic liquid crystal property and thermal stability below 230 °C. Alkoxyethyl β-D-glucopyranoside, as a class of sugar-based surfactants, will be expected to be developed in a variety of practical application.

Effects of the compound system of alkali and alkyl glycosides on the stability of oil-in-water emulsions

The effects of Na2CO3, nonionic surfactant octyldecyl glucoside (APG0810), and inorganic salt addition on the water separation ratio and apparent viscosity of oil-in-water (O/W) emulsions were investigated. The influences of this compound system on the stability of the emulsion and its synergistic mechanism were also analyzed. Results revealed that in the first compound situation, when APG was selected as the main surfactant and had a concentration of 0.1%, the mass concentration of Na2CO3 was 0.4%, the emulsion exhibited the strongest stability, and the water separation ratio at 30 °C for 120 min was 20.3%. In the second compound situation, when Na2CO3 was used as the main surfactant and had a concentration of 0.1%, the mass concentration of APG was 0.4%, the emulsion displayed the strongest stability, and the water separation ratio at 30 °C for 120 min was 57.8%. The stability of the O/W emulsion increased with increased NaCl addition, and a higher salt concentration corresponded to a lower water separation ratio. After CaCl2 addition, the apparent viscosity of the emulsion increased sharply, and the O/W emulsion underwent phase inversion to become an water-in-oil (W/O) emulsion. Within the set mass concentration range, increased salt concentration caused the apparent viscosity of the W/O emulsion measured at 50 °C and 30 rpm to decrease gradually but still exceeded 1500 mPa·s.

Stereoselective synthesis of 2-deoxy-β-C-aryl/alkyl glycosides using Prins cyclization: Application in the synthesis of C-disaccharides and differently protected C-aryl glycosides

2-Deoxy-β-C-aryl/alkyl glycosides were synthesized from di-O-pivaloyl protected homoallylic alcohol derived from D-mannitol with various aldehydes via the Prins cyclization. The salient features of this methodology are high yields and excellent stereoselectivity. This method has also been successfully applied to the synthesis of differently protected 2-deoxy-β-C-aryl glycosides and C-disaccharides. One of the 2-deoxy-β-C-aryl glycosides was utilized as a glycosyl acceptor in the glycosylation to synthesize an O-linked disaccharides.

Heptyl vicianoside and methyl caramboside from sour star fruit

Two new alkyl glycosides, heptyl vicianoside (1) and methyl 2-O-β-d-fucopyranosyl-α-l-arabinofuranoside (methyl caramboside, 4), were isolated from the sour fruit of Averrhoa carambola L. (Oxalidaceae), along with octyl vicianoside (2), cis-3-hexenyl rutinoside (3), and methyl α-d-fructofuranoside (5). Their structures were determined by spectroscopic and chemical methods. Compounds 2, 3, and 5 were obtained from the genus Averrhoa for the first time. All the compounds were evaluated for in vitro α-glucosidase, pancreatic lipase, and acetylcholinesterase inhibitory activities, but none of them were potent.

\u03b2-Mannanase-catalyzed synthesis of alkyl mannooligosides

β-Mannanases catalyze the conversion and modification of β-mannans and may, in addition to hydrolysis, also be capable of transglycosylation which can result in enzymatic synthesis of novel glycoconjugates. Using alcohols as glycosyl acceptors (alcoholysis), β-mannanases can potentially be used to synthesize alkyl glycosides, biodegradable surfactants, from renewable β-mannans. In this paper, we investigate the synthesis of alkyl mannooligosides using glycoside hydrolase family 5 β-mannanases from the fungi Trichoderma reesei (TrMan5A and TrMan5A-R171K) and Aspergillus nidulans (AnMan5C). To evaluate β-mannanase alcoholysis capacity, a novel mass spectrometry-based method was developed that allows for relative comparison of the formation of alcoholysis products using different enzymes or reaction conditions. Differences in alcoholysis capacity and potential secondary hydrolysis of alkyl mannooligosides were observed when comparing alcoholysis catalyzed by the three β-mannanases using methanol or 1-hexanol as acceptor. Among the three β-mannanases studied, TrMan5A was the most efficient in producing hexyl mannooligosides with 1-hexanol as acceptor. Hexyl mannooligosides were synthesized using TrMan5A and purified using high-performance liquid chromatography. The data suggests a high selectivity of TrMan5A for 1-hexanol as acceptor over water. The synthesized hexyl mannooligosides were structurally characterized using nuclear magnetic resonance, with results in agreement with their predicted β-conformation. The surfactant properties of the synthesized hexyl mannooligosides were evaluated using tensiometry, showing that they have similar micelle-forming properties as commercially available hexyl glucosides. The present paper demonstrates the possibility of using β-mannanases for alkyl glycoside synthesis and increases the potential utilization of renewable β-mannans.

CO2 as versatile carbonation agent of glycosides: Synthesis of 5- and 6-membered cyclic glycocarbonates and investigation of their ring-opening

This study demonstrates the successful use of CO2 as versatile carbonation agent for the synthesis of 5-membered and 6-membered bicyclic glycocarbonates from methyl α-d-mannopyranoside (MDM) and methyl α-d-galactopyranoside (MDG). On the one hand, these two sugars were cyclized into 5-membered glycocarbonates by mere reaction of CO2 with their hydroxyls either at cis-2,3 or cis-3,4 positions and without resorting to phosgene or its derivatives. The reactivity of the obtained 5-membered cyclic glycocarbonates were further tested with hexyl- and dodecyl amine. The self-assembling behavior of the formed alkyl glycosides in water was investigated and characterized by transmission electron microscope (TEM).On the other hand, secondary hydroxyls at 2- and 3- positions in MDM and MDG were first protected by a ketal group and by two ether, respectively before subjecting their respective 6-position hydroxyl to bromination. Their respective 6-bromo and 4-hydroxyl functions were subsequently reacted in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and CO2. The resulting 6-membered cyclic glycocarbonates were then polymerized using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) or DBU as organocatalyst. All the synthesized 5- and 6-membered cyclic glycocarbonates and polyglycocarbonates were thoroughly characterized by FT-IR, 1H, 13C NMR and MALDI-ToF and Gel Permeation Chromatography (GPC).

Conversion of Cellulose into Amphiphilic Alkyl Glycosides Catalyzed by Aquivion, a Perfluorosulfonic Acid Polymer.

The perfluorosulfonic acid (PFSA) Aquivion PW98 is an amphiphilic solid superacid which is shown to catalyze the conversion of cellulose into amphiphilic alkyl glycosides (AAGs) in 85 % yield (with 97 % selectivity). The process involves a mechanocatalytic depolymerization of cellulose followed by a direct glycosylation with n-dodecanol. In comparison to H2 SO4 and solid acid catalysts commonly employed in cellulose processing, Aquivion PFSA PW98 is not only recyclable but also exhibits superior catalytic performances in terms of yield, selectivity, and reactor productivity.

Purification and characterization of the colicin A immunity protein in detergent micelles

The immunity proteins against pore-forming colicins represent a family of integral membrane proteins that reside in the inner membrane of producing cells. Cai, the colicin A immunity protein, was characterized here in detergent micelles by circular dichroism (CD), size exclusion chromatography, chemical cross-linking, nuclear magnetic resonance (NMR) spectroscopy, cysteine accessibility, and colicin A binding in detergent micelles. Bile-salt derivatives induced extensive protein polymerization that precluded further investigation. The physical characterization of detergent-solubilized protein indicates that phosphate-containing detergents are more efficient in extracting, solubilizing and maintaining Cai in a monomeric state. Yet, their capacity to ensure protein activity, reconstitution, helix packing, and high-quality NMR spectra was inferior to that of milder detergents. Solvent ionic strength and composition greatly modified the solubilizing capacity of milder detergents. Most importantly, binding to the colicin A pore-forming domain (pf-ColA) occurred almost exclusively in sugar-derived detergents. The relative performance of the different detergents in each experiment depends on their impact not only on Cai structure, solubility and oligomerization state, but also on other reaction components and technical aspects. Thus, proteoliposomes were best obtained from protein in LDAO micelles, possibly also due to indirect effects on the lipidic bilayer. The compatibility of a detergent with Cai/pf-ColA complex formation is influenced by its effect on the conformational landscape of each protein, where detergent-mediated pf-ColA denaturation could also lead to negative results. The NMR spectra were greatly affected by the solubility, monodispersity, fold and dynamics of the protein-detergent complexes, and none of those tested here provided NMR spectra of sufficient quality to allow for peak assignment. Cai function could be proven in alkyl glycosides and not in those detergents that afforded the best solubility, reconstitution efficiency or spectral quality indicating that these criteria cannot be taken as unambiguous proof of nativeness without the support of direct activity measurements.

Synthesis and properties of alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranoside

A class of novel sugar-based surfactants named alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranosides were constructed by the introduction of oxyethene fragment (-OCH2CH2-) in the traditional alkyl glycoside structure. Such alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranosides with different length of alkyl chain were synthesized, and their single configurations were confirmed to be α-anomer by 1H NMR and HRMS analysis. Their water solubility, surface tension, emulsification, foaming and thermal stability were investigated, and the effect of alkyl chain length on their surface property was also compared. The water solubility of alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranoside was significantly superior to that of alkyl 2-acetamido-2-deoxy-α-D-glucopyranoside without an oxyethene fragment. Their dissolution process was an endothermic process and was driven by entropy increment as well. Alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranoside was disclosed to reduce significantly the surface tension of water. For both of CMC and γCMC, there was a decreasing trend with increasing of alkyl chain length. As increasing of alkyl chain length, the maximum surface adsorption (Γmax) increased and the molecular cross-sectional area (Amin) decreased. They adsorbed preferentially on the solution surface and then formed spontaneously micelles in solution by the hydrophobic effect. Nonyloxyethyl 2-acetamido-2-deoxy-α-D-glucopyranoside had the best foaming and emulsifying properties. All glycosides are thermally stable below 270°C. In view of the improvement of the water solubility and maintainance of surface activity with the introduction of the hydrophilic spacer, the novel alkoxyethyl 2-acetamido-2-deoxy-α-D-glucopyranoside should be expected to develop further its multiple applications as a class of novel water-soluble sugar-based surfactants in the future.

Direct Conversion of Cellulose into Alkyl Glycoside Surfactants

AbstractThe one‐step production of biodegradable alkyl glycoside (1‐dodecyl mono‐ and oligoglucoside) surfactants from cellulose has been achieved by direct alcoholysis in fatty alcohol media under Brønsted acid catalysis at near‐ambient pressure. The fatty alcohol serves as both solvent and reagent. Addition of small amounts of water prevents dehydration events and thus minimises product and solvent degradation. Furthermore, high initial cellulose loadings and short thermal cycles enable moderate‐to‐high conversions and selectivities (up to ≈ 70 %), and low solvent‐to‐product ratios.

Ring opening of epoxidized methyl or ethyl oleate by alkyl glycosides

Epoxidized methyl or ethyl oleate were used as models of FAtty Methyl Esters to explore their functionalization via ring opening of the internal epoxide by alkyl glycosides. Overcoming solubility issues, medium to long‐chain alkyl glucosides gave better results than methyl glucoside. Er(OTf)3 turned out to catalyze at room temperature the selective formation of hydroxyalkylethers with good yields versus transesterification, despite the concomitant formation of fatty ketones. A brief scope of the reaction, using several available alkyl glycosides, suggests that the strategy can easily lead to new highly functionnalized amphiphilic compounds, potential precursors for biobased materials.Practical applications: Interested in the formation of original high‐value intermediates from renewable materials, we tackled the reaction of unprotected carbohydrates and unsaturated vegetal oils featuring an internal epoxide. After ring‐opening, the obtained highly functionalized polyols are potential precursors to produce new biobased polymers, lubricants or surface‐active compounds for high‐value cosmetic or biopharmaceutical formulations.The formation of hydroxyalkylethers from epoxidized fatty esters and alkyl glycosides are catalyzed by Er(OTf)3 at room temperature with good yields and high selectivity versus transesterification.

D3h -Symmetrical Shape-Persistent Macrocycles Consisting of Pyridine-Acetylene-Phenol Conjugates as an Efficient Host Architecture for Saccharide Recognition.

Hexagonal shape-persistent macrocycles (SPMs) consisting of three pyridine and three phenol rings linked with acetylene bonds were developed as a preorganized host for saccharide recognition by push-pull-type hydrogen bonding. Three tert-butyl or 2,4,6-triisopropylphenyl substituents were introduced on the host to suppress self-aggregation by steric hindrance. In spite of the simple architecture, association constants Ka of the host with alkyl glycoside guests reached the order of 106 m-1 on the basis of UV/Vis titration experiments. This glycoside recognition was much stronger than that in the cases of acyclic equivalent hosts because of the entropic advantage brought by preorganization of the hydrogen-bonding sites. Solid-liquid extraction and liquid-liquid transport through a liquid membrane were demonstrated by using native saccharides, and much preference to mannose was observed.

Semicontinual synthesis of alkyl galactosides using β-galactosidase entrapped in polyvinylalcohol hydrogel

Fungal β-galactosidase from Aspergillus oryzae was immobilized into polyvinylalcohol (PVA) hydrogel by LentiKats® technology and used for the production of short-chain alkyl glycosides. Ethyl- and propyl-β-d-galactopyranosides were prepared from lactose (100 g/L) and varying initial amounts of alcohol (10–30% v/v) at 40 °C and pH 4.5. The entrapped β-galactosidase preserved 50% of the initial transgalactosylation activity after 25 repeated cycles in the production of ethyl β-d-galactopyranoside. When 5% (v/v) propanol was used as an acceptor, the enzyme activity (30–32 U/g immobilized enzyme) remained constant for 25 repeated batch runs. These findings suggest that entrapped β-galactosidase into LentiKats® has a great potential to be one effective, reusable and easy producible biocatalyst for the production of alkyl glycosides in a large scale.

Efficient isomerization of methyl arabinofuranosides into corresponding arabinopyranosides in presence of pyridine

Fisher glycosylation, the oldest but efficient reaction towards alkyl glycosides, suffers nonetheless from lack of selectivity, especially when dealing with pentoses. In this case, a mixture of the four isomers, namely the furanosides and the pyranosides, is formed. According to previous studies, the rate and selectivity of the reaction depend greatly on the reaction time and the temperature. In this report, another factor was evaluated, the introduction of a weak nucleophilic base. Interestingly, addition of pyridine few hours after the reaction has started allowed rapid isomerization of the methyl pentofuranosides into its pyranoside counterparts. The reaction proceeds with great diastereoselectivity using arabinose, ribose, xylose and lyxose as starting pentoses. Corresponding methyl pyranosides were obtained as the sole isomers with yields ranging from 65% to 75%.

Structural identification of alkyl glycosides obtained from the conversion of canna starch by immobilized α‐amylase from Aspergillus oryzae

In this study, a novel route using immobilized α‐amylase from Aspergillus oryzae as a catalyst for the preparation of alkyl glycosides (AGlys) from canna starch and methanol in water has been demonstrated. The effects of the experimental conditions on the conversion yield of AGlys were investigated. The optimized conditions were a canna starch concentration of 100 g/L, an enzyme concentration of 82.8 U/mL, and a reaction time of 24 h. A crude yield of 2.01% of AGlys was obtained under the optimal experimental conditions corresponding to an in‐between situation of a donor‐limiting and an acceptor‐limiting regime. The products were then characterized by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). The results showed that methyl‐maltoside was the major product of the alcoholysis reaction.

Enzymatic synthesis of propyl-α-glycosides and their application as emulsifying and antibacterial agents

Alkyl glycosides have been effectively used in many industries because of their biodegradable, emulsification and antibacterial properties. In this study, the alkyl glycoside of propyl glycosides (PGn) was synthesized using β-cyclodextrin (β-CD) and 1-propanol through the transglycosylation reaction of recombinant cyclodextrin glycosyltransferase (CGTase) from the Bacillus circulans A11. The optimal condition for the synthesis of propyl glycosides consisted of an incubation of 1.5% (w/v) β-CD and 500 U/mL of CGTase in a water/propanol content containing 10% (v/v) 1-propanol at pH 6.0, 50°C for 96 h. Upon analysis of the product at the optimal condition by TLC, at least three products which move faster than glucose were observed. These transferred products were formed with molecular weights of 222.1, 384.1 and 546.4 daltons as determined by mass spectrometry analysis; these values were in accordance with propyl glucoside (PG1), propyl maltoside (PG2) and propyl maltotrioside (PG3), respectively. PG1 and PG2 were produced and prepared on a large scale and subsequently purified by preparative TLC. The combined 1H- and 13C-NMR analysis confirmed that the structures of PG1 and PG2 were propyl-α-D-glucopyranoside and propyl-α-D-maltopyranoside, respectively. Both PG1 and PG2 showed emulsification activity and stability in their formation in water and n-hexadecane. Furthermore, the antibacterial activity of both products was determined and it was found that PG2 had a higher antibacterial activity against Staphylococcus aureus and Escherichia coli than that of PG1.

The Pyranoside-into-Furanoside Rearrangement of Alkyl Glycosides: Scope and Limitations

The pyranoside-into-furanoside (PIF) rearrangement was recently reported as a useful tool for the synthesis of furanoside-containing complex oligosaccharides. Until now, this transformation has only been described for some protected allyl-β- d -galactosides and one l -fucoside. In this communication its applicability is expanded. The formation of furanosides was observed under acid-promoted sulfation for a series of galactosides with varying alkyl substituents at the anomeric position as well as for several fucosides and glucosides. Meanwhile, furanoside formation was not detected in the case of mannopyranosides. The different reactivity of substrates was explained by values of activation barriers of endocyclic C1–O5 bond cleavage calculated by ab initio RHF methods. The reported results clarify the scope and limitations of the PIF rearrangement, which is important for its application in the synthesis of carbohydrate structures of practical meaning.