The formation of hex-5-enopyranosides and their selective hydrolysis in methylated polysaccharides

1978 ◽  
Vol 56 (5) ◽  
pp. 680-684 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Karl-Gunnar Rosell
Keyword(s):  
Uronic Acid ◽  
Gum Arabic ◽  
Hydroxyl Groups ◽  
Triphenyl Phosphite ◽  
Reaction Sequence ◽  
Selective Hydrolysis ◽  
Acidic Polysaccharides ◽  
Hydrolysis Of ◽  
Derivatives Of

The introduction of hex-5-enopyranoside residues into methylated acidic polysaccharides is effected by reduction of uronic acid residues, followed by reaction with triphenyl phosphite methiodide, and dehydroiodination. The selective hydrolysis of hex-5-enopyranosidic linkages with characterization of the 6-deoxyglycos-5-uloses thus formed and location of the aglyconic hydroxyl groups thus exposed has been demonstrated for methylated derivatives of birch xylan and gum arabic. The reaction sequence provides a new method for linkage analysis of acidic polysaccharides.

scholarly journals The selective cleavage of glycopyranosiduronamide linkages in methylated polysaccharides

1978 ◽  
Vol 56 (5) ◽  
pp. 685-690 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Karl-Gunnar Rosell
Keyword(s):  
Uronic Acid ◽  
Capsular Polysaccharide ◽  
Gum Arabic ◽  
Hydroxyl Groups ◽  
Selective Degradation ◽  
Derivatives Of

Hofmann degradation of glycosiduronamide linkages in methylated polysaccharides furnishes pentodialdose derivatives to which any sugar residues external to uronic acid residues remain attached together with degraded methylated polysaccharides carrying aglyconic hydroxyl groups. The selective degradation has been carried out on methylated derivatives of birch xylan, gum arabic, and the capsular polysaccharide from Klebsiella type 47. Procedures for the degradation of methylated polysaccharides in the vicinity of uronic acid residues are assessed.

The selective cleavage of permethylated glycopyranosiduronic acid linkages by oxidative decarboxylation with lead tetraacetate

1981 ◽  
Vol 59 (6) ◽  
pp. 935-940 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Hany Kamal Fanous ◽  
Nimal Savitri Kumar ◽  
Velupillai Puvanesarajah
Keyword(s):  
Sodium Borohydride ◽  
Gum Arabic ◽  
Lead Tetraacetate ◽  
Oxidative Decarboxylation ◽  
Hydroxyl Groups ◽  
Reaction Sequence ◽  
Pectic Acid ◽  
Acid Methyl ◽  
Sterculia Urens ◽  
Derivatives Of

Reaction of permethylated glycopyranosiduronic acids with lead tetraacetate furnishes epimeric 5-acetoxypentopyranosides as products of oxidative decarboxylation. Glycoside cleavage then occurs on treatment with sodium borohydride which affords the corresponding pentitols with exposure of aglyconic hydroxyl groups. The reaction sequence has been performed with permethylated derivatives of methyl β-melibiosiduronic acid, methyl β-gentiobiosiduronic acid, gum arabic, leiocarpan A, Sterculia urens gum, and citrus pectic acid. The scope of the reaction sequence in polysaccharide studies is discussed.

Aminoglycoside antibiotics: The formation and characterization of dihydrooxazine derivatives in the paromomycin series

1978 ◽  
Vol 56 (11) ◽  
pp. 1492-1499 ◽  
Author(s):  
Stephen Hanessian ◽  
Robert Massé ◽  
Goran Ekborg
Keyword(s):  
Chemical Modification ◽  
Zinc Chloride ◽  
Aminoglycoside Antibiotics ◽  
High Yield ◽  
Hydroxyl Groups ◽  
Model Studies ◽  
Derivatives Of ◽  
Excess Zinc ◽  
Chemical Evidence

Treatment of penta-N-benzyloxycarbonylparomomycin with benzaldehyde and excess zinc chloride gives a dibenzylidene derivative in high yield. This consists of the 4′,6′-O-benzylidene 4′′′,6′′′-N,O-benzylidene (dihydrooxazine) derivative of penta-N-benzyloxycarbonylparomomycin. Chemical evidence is presented to support this structure and model studies are reported for the formation of dihydrooxazine and oxazolidine derivatives of benzyloxycarbonylamino sugars containing suitably situated hydroxyl groups. The easily obtained dihydrooxazine derivative of paromomycin constitutes an interesting, preferentially blocked derivative, that is useful for the chemical modification of the parent antibiotic.

Structure of the Capsular Polysaccharide of Klebsiella K-type 56

1973 ◽  
Vol 51 (18) ◽  
pp. 3021-3026 ◽  
Author(s):  
Yuen-Min Choy ◽  
Guy G. S. Dutton
Keyword(s):  
Uronic Acid ◽  
Capsular Polysaccharide ◽  
Periodate Oxidation ◽  
Side Chain ◽  
Partial Hydrolysis ◽  
Hydrolysis Of

Methylation, periodate oxidation, and partial hydrolysis studies on the capsular polysaccharide of Klebsiella K-type 56 show the structure to be a repeating unit consisting of[Formula: see text]The nature of the anomeric linkages was determined by p.m.r. spectroscopy of isolated oligosaccharides. The position of the L-rhamnose side chain was defined by characterization of the di- and tetrasaccharides obtained by partial hydrolysis of the fully methylated polysaccharide.This structure represents the first capsular polysaccharide lacking uronic acid to be studied in the genus Klebsiella.

Synthesis and Characterization of TiO2/ PSt/PVP Multilayer Core-Shell Hybrid Microspheres

2012 ◽  
Vol 512-515 ◽  
pp. 2443-2447 ◽  
Author(s):  
Li Ying Guo
Keyword(s):  
Decomposition Temperature ◽  
Tetrabutyl Titanate ◽  
Core Shell ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Ft Ir ◽  
Hydrolysis Of ◽  
Thermal Stability Of

Multiplayer core-shell TiO2/PSt/PVP hybrid microspheres were successfully synthesized by the copolymerization of vinylpyrrolidone in the solution of ethyl acetate with TiO2/PSt core-shell hybrid microspheres which were formed through the encapsulation of KH570-g-TiO2 sol particles with styrene, while the active KH570-g-TiO2 sol particles were prepared by the hydrolysis condensation of KH-570 with tetrabutyl titanate. Characterization technologies of FT-IR and TGA were applied to investigate the structure and the thermal stability of the product. The results showed that the hydroxyl groups from the hydrolysis of KH-570 condensed with the surface hydroxyl groups of TiO2, as well as PSt and PVP were grafted successively onto the surface of KH570-g-TiO2 sol particles. The thermal decomposition temperature of TiO2/PSt/PVP was higher than TiO2/PSt, which also indicated that the obtained product was the final objective product.

scholarly journals Fine Modulation of the Catalytic Properties of Rhizomucor miehei Lipase Driven by Different Immobilization Strategies for the Selective Hydrolysis of Fish Oil

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 545 ◽  
Author(s):  
Maryam Yousefi ◽  
Marzia Marciello ◽  
Jose Manuel Guisan ◽  
Gloria Fernandez-Lorente ◽  
Mehdi Mohammadi ◽  
...  
Keyword(s):  
Fish Oil ◽  
Catalytic Properties ◽  
Iminodiacetic Acid ◽  
Rhizomucor Miehei ◽  
Rhizomucor Miehei Lipase ◽  
Selective Hydrolysis ◽  
Specific Activities ◽  
Miehei Lipase ◽  
Hydrolysis Of ◽  
Derivatives Of

Functional properties of each enzyme strictly depend on immobilization protocol used for linking enzyme and carrier. Different strategies were applied to prepare the immobilized derivatives of Rhizomucor miehei lipase (RML) and chemically aminated RML (NH2-RML). Both RML and NH2-RML forms were covalently immobilized on glyoxyl sepharose (Gx-RML and Gx-NH2-RML), glyoxyl sepharose dithiothreitol (Gx-DTT-RML and Gx-DTT-NH2-RML), activated sepharose with cyanogen bromide (CNBr-RML and CNBr-NH2-RML) and heterofunctional epoxy support partially modified with iminodiacetic acid (epoxy-IDA-RML and epoxy-IDA-NH2-RML). Immobilization varied from 11% up to 88% yields producing specific activities ranging from 0.5 up to 1.9 UI/mg. Great improvement in thermal stability for Gx-DTT-NH2-RML and epoxy-IDA-NH2-RML derivatives was obtained by retaining 49% and 37% of their initial activities at 70 °C, respectively. The regioselectivity of each derivative was also examined in hydrolysis of fish oil at three different conditions. All the derivatives were selective between cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) in favor of EPA. The highest selectivity (32.9 folds) was observed for epoxy-IDA-NH2-RML derivative in the hydrolysis reaction performed at pH 5 and 4 °C. Recyclability study showed good capability of the immobilized biocatalysts to be used repeatedly, retaining 50–91% of their initial activities after five cycles of the reaction.

scholarly journals Identification of Novel Gymnodimines and Spirolides from the Marine Dinoflagellate Alexandrium ostenfeldii

Marine Drugs ◽  
2018 ◽  
Vol 16 (11) ◽  
pp. 446 ◽  
Author(s):  
Christian Zurhelle ◽  
Joyce Nieva ◽  
Urban Tillmann ◽  
Tilmann Harder ◽  
Bernd Krock ◽  
...  
Keyword(s):  
Chemical Diversity ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Alexandrium Ostenfeldii ◽  
Exocyclic Methylene ◽  
Polyketide Chain ◽  
Marine Dinoflagellates ◽  
Toxin Class ◽  
Derivatives Of

Cyclic imine toxins are neurotoxic, macrocyclic compounds produced by marine dinoflagellates. Mass spectrometric screenings of extracts from natural plankton assemblages revealed a high chemical diversity among this toxin class, yet only few toxins are structurally known. Here we report the structural characterization of four novel cyclic-imine toxins (two gymnodimines (GYMs) and two spirolides (SPXs)) from cultures of Alexandrium ostenfeldii. A GYM with m/z 510 (1) was identified as 16-desmethylGYM D. A GYM with m/z 526 was identified as the hydroxylated degradation product of (1) with an exocyclic methylene at C-17 and an allylic hydroxyl group at C-18. This compound was named GYM E (2). We further identified a SPX with m/z 694 as 20-hydroxy-13,19-didesmethylSPX C (10) and a SPX with m/z 696 as 20-hydroxy-13,19-didesmethylSPX D (11). This is the first report of GYMs without a methyl group at ring D and SPXs with hydroxyl groups at position C-20. These compounds can be conceived as derivatives of the same nascent polyketide chain, supporting the hypothesis that GYMs and SPXs are produced through common biosynthetic genes. Both novel GYMs 1 and 2 were detected in significant amounts in extracts from natural plankton assemblages (1: 447 pg; 2: 1250 pg; 11: 40 pg per mL filtered seawater respectively).

Synthesis of 4-O- and 6-O-monoacryloyl derivatives of sucrose by selective hydrolysis of 4,6-O-(1-ethoxy-2-propenylidene)sucrose. Polymerization and copolymerization with styrene

1993 ◽  
Vol 240 ◽  
pp. 143-152 ◽  
Author(s):  
Elisabeth Fanton ◽  
Catherine Fayet ◽  
Jacques Gelas ◽  
Alain Deffieux ◽  
Michel Fontanille ◽  
...  
Keyword(s):  
Selective Hydrolysis ◽  
Hydrolysis Of ◽  
Derivatives Of

scholarly journals Polysaccharide Based Polymers Produced by Scabby Cankered Cactus Pear (Opuntia ficus-indica L.) Infected by Neofusicoccum batangarum: Composition, Structure, and Chemico-Physical Properties

Biomolecules ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Gabriella Santagata ◽  
Alessio Cimmino ◽  
Giovanni Dal Poggetto ◽  
Domenico Zannini ◽  
Marco Masi ◽  
...  
Keyword(s):  
Solid State Nmr ◽  
Uronic Acid ◽  
Research Work ◽  
Cactus Pear ◽  
Opuntia Ficus Indica ◽  
Hplc Profile ◽  
Composition Structure ◽  
Tlc Analysis ◽  
Hydrolysis Of

Neofusiccocum batangarum is the causal agent of scabby canker of cactus pear (Opuntia ficus-indica L.). The symptoms of this disease are characterized by crusty, perennial cankers, with a leathery, brown halo. Characteristically, a viscous polysaccharide exudate, caking on contact with air, leaks from cankers and forms strips or cerebriform masses on the surface of cactus pear cladodes. When this polysaccharide mass was partial purified, surprisingly, generated a gel. The TLC analysis and the HPLC profile of methyl 2-(polyhydroxyalkyl)-3-(o-tolylthiocarbomoyl)-thiazolidine-4R-carboxylates obtained from the mixture of monosaccharides produced by acid hydrolysis of the three EPSs examined in this research work [the polysaccharide component of the exudate (EPSC) and the EPSs extracted from asymptomatic (EPSH) and symptomatic (EPSD) cladodes] showed the presence of d-galactose, l-rhamnose, and d-glucose in a 1:1:0.5 ratio in EPSC while d-galactose, l-rhamnose, d-glucose, and d-xylose at the same ratio were observed in EPSH and EPSD. The presence of uronic acid residues in EPSC was also showed by solid state NMR and IR investigation. Furthermore, this manuscript reports the chemical-physical characterization of the gel produced by the infected cactus pear.

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