Synthesis of sugar oxime ether surfactants

A straightforward synthesis of a novel class of sugar surfactants is described. The key step is the chemoselective condensation of a hydrophobic alkoxyamine with the resident aldehyde/ketone moiety on a hydrophilic sugar. Neither protection/deprotection of the sugars nor extensive product purification is required. The method allows for the facile adjustment of hydrophobic and hydrophilic domains of the sugar oxime ether surfactant and uses inexpensive, readily accessible, and renewable materials.     

Chemoselective coupling of sugar oximes and α-ketoacids to glycosyl amides and N-glycopeptides

The reaction of unprotected sugar hydroxylamines and oximes with α-ketoacids leads to the chemoselective formation of glycosyl amides following the decarboxylative condensation pathway of Bode’s ketoacid hydroxylamine (KAHA) ligation. Sugar oximes with gluco configuration stereoselectively form β-linked products. This method can be used for the convergent synthesis of N-acylated sugars and oligosaccharides bearing small labels, spacers, or peptides in the acyl part.     

Addressing the scope of the azide-nitrile cycloaddition in glycoconjugate chemistry. The assembly of C-glycoclusters on a calix[4]arene scaffold through tetrazole spacers

New glycoclusters constituted of ribosylmethyl, galactosylmethyl, and glucosylmethyl fragments assembled on a calix[4]arene platform by means of propoxytetrazole spacers have been prepared by coupling the corresponding sugar azides with p-toluenesulfonyl cyanide, and then reacting 1-glycosylmethyl-5-sulfonyl-tetrazole derivatives thus formed with a calix[4]arene tetrol.     

New polycationic polynorbornene latexes bearing an amphiphilic sugar corona of counterions: synthesis and complexation with DNA

A new family of polycationic polynorbornene with ω-gluconamidoalkanoates and ω-lactobionamidoalkanoates as amphiphilic counterions has been prepared. These polymers spontaneously form stable latexes in water with an amphiphilic sugar corona around the particles. With these counterions, the sugar moieties are separated from the surface of latex particles by the aminoalkanoic acid residue and consequently are remote from the surface of such latexes. Such location of sugar may promote their stronger interaction with cell receptors. These original amphiphilic compartmentalized surface polycationic latexes are able to bind and efficiently complex DNA in very small complexes. Furthermore, because of the effect of the sugar corona on the formation of the complexes, there is only a slight influence of the hydrophobicity of the counterions on DNA packing.     

Efficient photocatalytic treatment of sugar mill wastewater with 2%Ag3PO4/Fe/GTiP nanocomposite

The large amount of colored substances exist in the sugar mills wastewater that give higher organic load to the effluent. Therefore, a novel study of sugar mill wastewater treatment was carried out under photocatalysis by using a nanocomposite of silver phosphate-iron-graphene oxide-titanium phosphate (Ag₃PO₄/Fe/GTiP). The catalyst was prepared by simple chemical process with 2% content of Ag₃PO₄ to Fe/GTiP. The light, catalyst dosage, pH, and scavenger impacts on the decolorization and chemical oxygen demand (COD) removal from the sugar mill wastewater were observed. The highest decolorization and COD removal of 85.02% and 80.3% was achieved under pH-1 by using 50 W visible halogen light at catalyst dosage of 100 mg/75 ml in 200 min. The excellent recycled results were observed up to four cycles. The obtained results proves that this catalyst has high photocatalytic efficiency to treat the sugar mill wastewater.     

An environmentally benign and practical synthesis of sugar orthoesters promoted by potassium fluoride

An extremely practical method for synthesis of sugar orthoesters has been developed without using any organic amines or heavy metals as additives. Various sugar orthoesters were prepared in good yields by the reaction of an acylated glycosyl bromide and an alcohol in the presence of potassium fluoride.     

2,3,6-Trideoxy sugar nucleotides: synthesis and stability

The synthesis and characterization of highly challenging 2,3,6-trideoxy sugar nucleotides were described for the first time. The study of their hydrolysis kinetics in aqueous buffers provided insight into their application as glycosyl donors.     

Synthesis, structure, and sugar dynamics of a 2′-spiroisoxazolidine thymidine analog

Bicyclic nucleoside analogs have shown promise in Antisense and RNA interference strategies. Ribofuranosyl ring conformation is a controlling factor in this regard. We have introduced a spiroisoxazolidine ring at the 2′-position of the sugar to gauge the effect it has on sugar dynamics. Proton relaxation measurements and coupling constant analysis indicate the sugar is locked in the North conformation with substantial sugar rigidity evident.     

Synthesis and structural studies of peptides containing a glucose-derived furanoid sugar amino acid

Conformational analysis of peptides containing a glucose-derived furanoid sugar amino acid (Gaa) by detailed NMR and constrained MD studies revealed that peptides with repeating Gaa-Leu-Val units had conformational signatures very similar to those of linear homooligomers of Gaa.     

Synthesis of cyclic oligomers of a modified sugar amino acid utilising dynamic combinatorial chemistry

Dynamic combinatorial chemistry has been utilised for the rapid synthesis of a library of cyclic oligomers based on a modified furanoid sugar amino acid repeat unit.     

Emulsifying properties and functional compositions of sugar beet pectins extracted under different conditions

Extraction conditions have important effects on the characteristics of sugar beet pectin (SBP). Response surface methodology (RSM) was used to study the impact of different extraction parameters on pectin yield, protein, ferulic acid, and galacturonic acid contents as well as on the emulsifying properties. Results indicated that pH was the main factor influencing pectin yield (ranging from 6.7 to 24.6%). Protein content varied from 0.5 to 6%, while ferulic acid content (ranging from 1.55 to 2.42%) was slightly influenced by the extraction conditions. Droplet sizes of the emulsions stabilized by different SBPs varied from 1.12 to 4.12 µm. Furthermore, according to the correlation analysis, protein content–pectin yield and ferulic acid–pectin yield demonstrated good correlations, respectively. Based on the present study, SBP with different functional components could be extracted as per relevant practical objectives.     

New synthetic approaches to sugar ureas. Access to ureido-β-cyclodextrins

An efficient method for the preparation of urea-bridged cyclodextrins using triphosgene in the isocyanation step in an aqueous two-phase system is reported. Per-O-acetylated glycopyranosylamines and 2-amino-2-deoxy-α and β-d-glucose were also transformed into the corresponding isocyanates using either an aqueous two-phase or an anhydrous dichloromethane medium, and converted in situ into ureas. An alternative method for the preparation of sugar-derived ureas consisting of desulfurization of sugar thioureas with mercury oxide is also presented.     

Synthesis of branched aminopolysaccharides by acid-catalyzed polymerization of sugar oxazoline monomer

Acid-catalyzed polymerization of a sugar oxazoline monomer 1b having two free hydroxy groups was carried out to produce a branched aminopolysaccharide 2b. The reaction proceeded via the stereoregular glycosylation through oxazoline ring-opening process, giving rise to 2b consisting of β-glycosidic linkages. The structure of 2b was determined by the ¹H NMR, ¹³C NMR, and IR spectra. The molecular weights determined by GPC measurements were 4200-6100. The degrees of branching were estimated by the ¹H NMR spectra of the products by the reaction of 2b with 3,5-dinitrobenzoyl chloride. Deprotection of 2b was carried out by the catalytic hydrogenation in the presence of 10% Pd-C to produce a free branched aminopolysaccharide.     

Stereoselective synthesis of the various isomers of 3,4-dideoxy furanoid sugar amino acids with methyl substitution at the C6 position

Various isomers of C6-methyl-containing chiral 3,4-dideoxy furanoid sugar amino acids were synthesized following a common strategy, in which the C2 and C6 chiral centres were derived from the chiralities of the two starting materials, glyceraldehyde acetonide and N,N-dibenzylalaninal, respectively, and the C5 centre was fixed by standard diastereoselective transformations.     

Conformational studies of the linear homooligomers of a glucose-derived furanoid sugar amino acid

Conformational analysis of the linear tetramer of the glucose-derived furanoid sugar amino acid 1 by NMR and constrained molecular dynamics studies revealed that the fully protected tetramer 2a has a well-defined structure in CDCl₃ with repeating β-turns, each involving a 10-membered ring structure with intramolecular hydrogen bonds between NH_i → CO_i−2. Its deprotected versions 2b and 2c showed aggregation in organic solvents with structures similar to that of 2a.     

Synthesis of a C3-symmetric macrocycle with alternating sugar amino acid and tyrosine residues

A C₃-symmetric macrocycle with alternating sugar amino acid and tyrosine residues was synthesized in seven steps from tyrosine tert-butyl ester and a sugar amino acid precursor derived from D-glucosamine. An Fmoc-protected D-glucosamine derivative was oxidized at C-6 to give the sugar amino acid, which was immediately coupled to tyrosine tert-butyl ester to produce an orthogonally protected building block. This building block was subsequently elongated to the trimer via the dimer, and finally cyclized to give the C₃-symmetric macrocycle.     

Characterization of methylcellulose produced from sugar cane bagasse cellulose: Crystallinity and thermal properties

In the present work, methylcellulose produced from sugar cane bagasse was characterized by FTIR, WAXD, DTA and TGA techniques. Two samples were synthesized: methylcellulose A and methylcellulose B. The only difference in the process was the addition of fresh reactants during the preparation of methylcellulose B. The ratio between the absorption intensities of the C-H stretching band at around 2900 cm⁻¹ and O-H stretching at around 3400 cm⁻¹ for methylcellulose B is higher than for methylcellulose A, indicating that methylcellulose B showed an increase in the degree of substitution (DS). Methylcellulose A presents a more heterogeneous structure, which is similar to the original cellulose as seen through FTIR and DTA. Methylcellulose B showed thermal properties similar to commercial methylcellulose. The modification of methylcellulose preparation method allows the production of a material with higher DS, crystallinity and thermal stability in relation to the original cellulose and to methylcellulose A.     

Copper determination in sugar cane spirits by fast sequential flame atomic absorption spectrometry using internal standardization

In this study, a fast and simple method is proposed for the determination of Cu in sugar cane spirits employing fast sequential flame atomic absorption spectrometry and the internal standard technique. First, Ag, Bi, Co and Ni were evaluated as internal standards to minimize transport interferences. The results demonstrated that Ag at a concentration of 2 mg L^− 1 was effective. Under these conditions, Cu could be determined with a limit of detection of 15 µg L^− 1. Then, Cu was determined in 5 sugar cane spirit samples using the proposed method and the results were compared with those obtained by inductively coupled plasma optical emission spectrometry after microwave oven acid digestion. The content of Cu varied from 0.66 to 6.64 mg L^− 1. Accuracy and precision of the proposed method were evaluated by comparing the results obtained with both methods. A paired t-test at a 95% confidence level showed that the proposed method enabled the achievement of similar results as those obtained by ICP OES after acid digestion.     

Spectrophotometric flow injection monitoring of sulfide during sugar fermentation

A spectrophotometric flow injection procedure involving N,N-dimethyl-p-phenylenediamine (DMPD) is applied to the sulfide monitoring of a sugar fermentation by Saccharomyces cerevisiae under laboratory conditions. The gaseous chemical species evolving from the fermentative process, mainly CO₂, are trapped allowing a cleaned sample aliquot to be collected and introduced into the flow injection analyzer. Measurement rate, signal repeatability, detection limit and reagent consumption per measurement were estimated as 150 h⁻¹, 0.36% (n = 20), 0.014 mg L⁻¹ S and 120 μg DMPD, respectively. The main characteristics of the monitoring record are discussed. The strategy is worthwhile for selecting yeast strain, increasing the industrial ethanol production and improving the quality of wines.     

Sc(OTf)3-catalyzed sugar based tandem ene-Prins cyclization: a novel synthesis of hexahydro-2H-furo[3,2-b]pyranopyran scaffolds

Ttandem ene-Prins cyclization between an aldehyde and an olefin tethered sugar aldehyde has been achieved using a catalytic amount of scandium triflate (10 mol %) at ambient temperature to give a novel series of sugar annulated pyranopyran derivatives in good yields with high selectivity. This is the first report on sugar based ene-Prins cyclization between an aldehyde and O-prenyl derivative of a sugar aldehyde.