1
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Sakai H, Tsushida S, Hosoya T, Miyafuji H. Role of ion pairs in model glycosylation reactions of permethylated glucosyl and xylosyl triflates. Carbohydr Res 2024; 544:109227. [PMID: 39142017 DOI: 10.1016/j.carres.2024.109227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Revised: 08/01/2024] [Accepted: 08/01/2024] [Indexed: 08/16/2024]
Abstract
Elucidating the molecular mechanisms of chemical O-glycosylation remains a significant challenge in glycochemistry. This study examines the mechanism of the nucleophilic substitution reaction between glycosyl triflates, which are extensively used in studies of glycosylation mechanisms, and several acceptor alcohols. The investigation was conducted through a comparative analysis of permethylated glucosyl triflate GTf and its xylosyl counterpart XTf. The glycosylation reactions, conducted in dichloromethane using GTf and XTf with EtOH, tBuOH, and CF3CH2OH, exhibited diverse α/β selectivities depending on the types of donor and acceptor molecules used. Identifying a unified mechanism to explain this range of selectivities proved challenging. Notably, we observed a distinct trend wherein the addition of excess triflate salt (Bu4NOTf) had a more pronounced effect on the α/β selectivity in glycosylation reactions utilizing XTf compared to those using GTf. Quantum chemical calculations performed at the SCS-MP2//DFT(M06-2X) level, with explicit inclusion of five solvent molecules, showed that contact ion pairs arising from XTf were significantly more stable than those from GTf. These experimental and computational results strongly suggest that ion pairs play a more crucial role in the glycosylation process involving XTf than GTf. Additionally, our quantum chemical analyses clarified that the enhanced stability of the ion pairs from XTf was attributed not to the strength of the C-1-OTf bond within XTf but to the flexibility in the conformational changes of XTf's pyranosyl ring.
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Affiliation(s)
- Hana Sakai
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1- 5 Shimogamo-hangi-cho, Sakyo-ku, Kyoto, 606-8522, Japan
| | - Sae Tsushida
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1- 5 Shimogamo-hangi-cho, Sakyo-ku, Kyoto, 606-8522, Japan
| | - Takashi Hosoya
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1- 5 Shimogamo-hangi-cho, Sakyo-ku, Kyoto, 606-8522, Japan.
| | - Hisashi Miyafuji
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1- 5 Shimogamo-hangi-cho, Sakyo-ku, Kyoto, 606-8522, Japan
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2
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Christophe G, Hou X, Petit E, Traikia M, Le Cerf D, Rihouey C, Gardarin C, Delattre C, Michaud P, Pierre G, Dubessay P. Description of the Wild Strain Rhizobium rosettiformans DSM26376, Reclassified under Peteryoungia rosettiformans comb.nov., for Producing Glucuronan. Polymers (Basel) 2023; 15:polym15092177. [PMID: 37177323 PMCID: PMC10180729 DOI: 10.3390/polym15092177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/12/2023] [Accepted: 04/28/2023] [Indexed: 05/15/2023] Open
Abstract
Glucuronan is a polysaccharide composed of β-(1,4)-linked d-glucuronic acids having intrinsic properties and biological activities recoverable in many fields of application. Currently, the description of Sinorhyzobium meliloti M5N1CS mutant bacterial strain as the sole source of glucuronan makes it relevant to the exploration of new microorganisms producing glucuronan. In this study, the Peteryoungia rosettifformans strain (Rhizobia), was identified as a wild producer of an exopolysaccharide (RhrBR46) related to glucuronan. Structural and biochemical features, using colorimetric assays, Fourier infrared spectroscopy, nuclear magnetic resonance, high pressure size exclusion chromatography coupled to multi-angle light laser scattering, and enzymatic assays allowed the characterization of a polyglucuronic acid, having a molecular mass (Mw¯) of 1.85 × 105 Da, and being partially O-acetylated at C-2 and/or C-3 positions. The concentration of Mg2+ ions in the cultivation medium has been shown to impact the structure of RhrBR46, by reducing drastically its Mw¯ (73%) and increasing its DA (10%). Comparative structural analyses between RhrBR46 and the glucuronan from Sinorhyzobium meliloti M5N1CS strain revealed differences in terms of molecular weight, degree of acetylation (DA), and the distribution of acetylation pattern. These structural divergences of RhrBR46 might contribute to singular properties or biological activities of RhrBR46, offering new perspectives of application.
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Affiliation(s)
- Gwendoline Christophe
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Xiaoyang Hou
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Emmanuel Petit
- UMRT INRAe 1158 BioEcoAgro, Laboratoire BIOPI, Institut Universitaire et Technologique, Université de Picardie Jules Verne, F-80025 Amiens, France
| | - Mounir Traikia
- CNRS, ICCF, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Didier Le Cerf
- Polymères Biopolymères Surfaces, Normandie Université, UNIROUEN, INSA Rouen, CNRS, UMR6270, F-76821 Mont Saint-Aignan, France
| | - Christophe Rihouey
- Polymères Biopolymères Surfaces, Normandie Université, UNIROUEN, INSA Rouen, CNRS, UMR6270, F-76821 Mont Saint-Aignan, France
| | - Christine Gardarin
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Cédric Delattre
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
- Institut Universitaire de France (IUF), 1 rue Descartes, F-75005 Paris, France
| | - Philippe Michaud
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Guillaume Pierre
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
| | - Pascal Dubessay
- Clermont Auvergne INP, CNRS, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France
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Ruda A, Widmalm G, Wohlert J. O-Methylation in Carbohydrates: An NMR and MD Simulation Study with Application to Methylcellulose. J Phys Chem B 2021; 125:11967-11979. [PMID: 34704449 PMCID: PMC8573740 DOI: 10.1021/acs.jpcb.1c07293] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
![]()
Methylated carbohydrates
are important from both biological and
technical perspectives. Specifically, methylcellulose is an interesting
cellulose derivative that has applications in foods, materials, cosmetics,
and many other fields. While the molecular dynamics simulation technique
has the potential for both advancing the fundamental understanding
of this polymer and aiding in the development of specific applications,
a general drawback is the lack of experimentally validated interaction
potentials for the methylated moieties. In the present study, simulations
using the GROMOS 56 carbohydrate force field are compared to NMR spin–spin
coupling constants related to the conformation of the exocyclic torsion
angle ω in d-glucopyranose and derivatives containing
a 6-O-methyl substituent and a 13C-isotopologue thereof.
A 3JCC Karplus-type relationship
is proposed for the C5–C6–O6–CMe torsion
angle. Moreover, solvation free energies are compared to experimental
data for small model compounds. Alkylation in the form of 6-O-methylation
affects exocyclic torsion only marginally. Computed solvation free
energies between nonmethylated and methylated molecules were internally
consistent, which validates the application of these interaction potentials
for more specialized purposes.
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Affiliation(s)
- Alessandro Ruda
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jakob Wohlert
- Department of Fiber and Polymer Technology, School of Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden.,Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
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4
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Thermal degradation of citrus pectin in low-moisture environment – Investigation of backbone depolymerisation. Food Hydrocoll 2020. [DOI: 10.1016/j.foodhyd.2020.105937] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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5
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Einhorn-Stoll U, Kastner H, Urbisch A, Kroh LW, Drusch S. Thermal degradation of citrus pectin in low-moisture environment - Influence of acidic and alkaline pre-treatment. Food Hydrocoll 2019. [DOI: 10.1016/j.foodhyd.2018.02.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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6
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Yoneda Y, Hettegger H, Rosenau T, Kawada T. Additive Tendency of Substituent Effects onto Rate Constant of Acidic Hydrolysis of Methyl 4-O-Methyl-β-d-Glucopyranoside. ChemistrySelect 2016. [DOI: 10.1002/slct.201601125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Yuko Yoneda
- College of Agriculture; Academic Institute; Shizuoka University, Ohya 836, Suruga-ku; Shizuoka 422-8529 Japan
| | - Hubert Hettegger
- Division of Chemistry of Renewable Resources; Department of Chemistry; University of Natural Resources and Life Sciences, Vienna (BOKU); Konrad-Lorenz-Strasse 24 A-3430 Tulln Austria
| | - Thomas Rosenau
- Division of Chemistry of Renewable Resources; Department of Chemistry; University of Natural Resources and Life Sciences, Vienna (BOKU); Konrad-Lorenz-Strasse 24 A-3430 Tulln Austria
| | - Toshinari Kawada
- Graduate School of Life and Environmental Sciences; Kyoto Prefectural University, Nakaragi-cho 1-5, Shimogamo, Sakyo-ku; Kyoto 606-8522 Japan
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7
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Phan HD, Yokoyama T, Matsumoto Y. Direct participation of counter anion in acid hydrolysis of glycoside. Org Biomol Chem 2012; 10:7382-91. [DOI: 10.1039/c2ob25451d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Heuckendorff M, Pedersen CM, Bols M. The influence of neighboring group participation on the hydrolysis of 2-O-substituted methyl glucopyranosides. Org Lett 2011; 13:5956-9. [PMID: 22007683 DOI: 10.1021/ol202308y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Does neighboring group participation actually enhance the reactivity of the anomeric center when the participating group is inherently disarming? To investigate the influence of the neighboring group effect from a 2-O protective group on acidic glycoside hydrolysis, 10 methyl glucosides having different protective groups on O2 have been synthesized and a clear trend between anomeric configuration, participation of the protective group, and the rate of hydrolysis could be observed.
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9
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Pilgrim W, Murphy PV. SnCl4- and TiCl4-Catalyzed Anomerization of Acylated O- and S-Glycosides: Analysis of Factors That Lead to Higher α:β Anomer Ratios and Reaction Rates. J Org Chem 2010; 75:6747-55. [DOI: 10.1021/jo101090f] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Wayne Pilgrim
- School of Chemistry, National University of Ireland, Galway, Ireland
- Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Paul V. Murphy
- School of Chemistry, National University of Ireland, Galway, Ireland
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10
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Stability studies of hydrazide and hydroxylamine-based glycoconjugates in aqueous solution. Carbohydr Res 2009; 344:278-84. [DOI: 10.1016/j.carres.2008.11.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 11/04/2008] [Accepted: 11/10/2008] [Indexed: 11/18/2022]
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11
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Rinaldi R, Schüth F. Acid hydrolysis of cellulose as the entry point into biorefinery schemes. CHEMSUSCHEM 2009; 2:1096-107. [PMID: 19950346 DOI: 10.1002/cssc.200900188] [Citation(s) in RCA: 308] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Cellulose is a major source of glucose because it is readily available, renewable, and does not compete with the food supply. Hydrolysis of cellulose is experiencing a new research and development cycle in which this reaction is carried out over solid catalysts and coupled to other reactions for increased efficiency. Cellulose is typically not soluble in conventional solvents and very resistant to chemical and biological transformations. This Review focuses on aspects related to the hydrolysis of cellulose as this process is a significant entry point into the biorefinery scheme based on carbohydrates for the production of biofuels and biochemicals. Structural features of cellulose, conventional acid-catalyzed reactions, and the use of solid acid catalysts for hydrolysis are discussed. The longterm success of the biorefinery concept depends on the development of energetically efficient processes to convert cellulose directly or indirectly into biofuels and chemicals.
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Affiliation(s)
- Roberto Rinaldi
- Department of Heterogeneous Catalysis, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
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12
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O'Brien C, Poláková M, Pitt N, Tosin M, Murphy PV. Glycosidation-anomerisation reactions of 6,1-anhydroglucopyranuronic acid and anomerisation of beta-D-glucopyranosiduronic acids promoted by SnCl(4). Chemistry 2007; 13:902-9. [PMID: 17086575 DOI: 10.1002/chem.200601111] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The reaction of silylated nucleophiles with 6,1-anhydroglucopyranuronic acid (glucuronic acid 6,1-lactones) catalysed by tin(IV) chloride provides 1,2-trans or 1,2-cis (deoxy)glycosides in a manner dependent on the donor structure. The alpha-glycoside was obtained for reactions of the donor with the 2-acyl group and 2-deoxydonors, whereas the 2-deoxy-2-iodo donor gave the beta-glycoside. Experimental evidence shows that when 1,2-cis-glycoside formation occurs, the anomerisation of initially formed 1,2-trans-glycosides catalysed by SnCl(4) is possible. The anomerisation of beta-D-glucopyranosiduronic acids was found to be faster, in some cases, than anomerisation of related beta-D-glucopyranosiduronic acid esters and beta-D-glucopyranoside derivatives and the rates are dependent on the structure of the aglycon. Moreover, the rates of anomerisation of beta-D-glucopyranuronic acid derivatives can be qualitatively correlated with rates of hydrolysis of beta-D-glucopyranosiduronic acids. Mechanistic possibilities for the reactions are considered.
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Affiliation(s)
- Colin O'Brien
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland
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13
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Cronin L, Tosin M, Müller-Bunz H, Murphy PV. The synthesis of cyclic imidates from amides of glucuronic acid and investigation of glycosidation reactions. Carbohydr Res 2007; 342:111-8. [PMID: 17123491 DOI: 10.1016/j.carres.2006.10.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 10/20/2006] [Accepted: 10/25/2006] [Indexed: 11/28/2022]
Abstract
The synthesis of novel cyclic glycosyl imidates and an investigation of their potential as donors in glycosidation reactions is described. The results show that 1,2-cis glycosides obtained from the reactions of glycosyl acetates or cyclic imidates, each derived from amides of glucuronic acid, result from the anomerisation of initially formed 1,2-trans glycosides.
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Affiliation(s)
- Linda Cronin
- UCD School of Chemistry and Chemical Biology, Centre for Synthesis and Chemical Biology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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14
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Tvaroska I, Taravel FR, Utille JP, Carver JP. Quantum mechanical and NMR spectroscopy studies on the conformations of the hydroxymethyl and methoxymethyl groups in aldohexosides. Carbohydr Res 2002; 337:353-67. [PMID: 11841816 DOI: 10.1016/s0008-6215(01)00315-9] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The potential energy surfaces of the hydroxymethyl and methoxymethyl groups in methyl hexopyranosides have been extensively studied, employing quantum mechanical calculations and high resolution NMR data. The structure and energy of the C-5-C-6 rotamers were calculated at the B3LYP level of the density functional theory (DFT). For all, geometry optimizations were carried out for 264 conformers of 16 methyl D-gluco- and methyl D-galactopyranoside derivatives 1-16 at the B3LYP/6-31G** level. For all calculated minima, single-point calculations were performed at the B3LYP/6-311++G** level. Solvent effects were considered using a self-consistent reaction field method. Values of the vicinal coupling constants 3J(H-5-H-6R), 3J(H-5-H-6S), 3J(C-4-H-6R), and 3J(C-4-H-6S) for methyl D-glucopyranosides, methyl D-galactopyranosides and their 6-O-methyl derivatives 9-16 were measured in two solvents, methanol and water. The calculated gg, gt, and tg rotamer populations of the hydroxymethyl and methoxymethyl groups in 9-16 agreed well with experimental data. The results clearly showed that the population of gg, gt, and tg rotamers is sensitive to solvent effects. It was concluded that the preference of rotamers in 1-16 is due to the hydrogen bonding and solvent effects.
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Affiliation(s)
- Igor Tvaroska
- GlycoDesign Inc., 480 University Avenue, Suite 400, Ont., M5G 1V2, Toronto, Canada
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15
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Namchuk MN, McCarter JD, Becalski A, Andrews T, Withers SG. The Role of Sugar Substituents in Glycoside Hydrolysis. J Am Chem Soc 2000. [DOI: 10.1021/ja992044h] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Evtushenko EV. Regioselective methylation of methyl glycopyranosides with diazomethane in the presence of transition-metal chlorides and of boric acid. Carbohydr Res 1999. [DOI: 10.1016/s0008-6215(99)00044-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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17
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Wessel HP, Bartsch S. Conformational flexibility in highly sulfated beta-D-glucopyranoside derivatives. Carbohydr Res 1995; 274:1-9. [PMID: 7585701 DOI: 10.1016/0008-6215(95)00131-c] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Triggered by findings on heparin-like disaccharides, the conformation of sulfated glucopyranosides was investigated. Sodium (methyl 2,3,4-tri-O-sulfonato-beta-D-glucopyranosid)uronate tetrasodium salt is in a conformational equilibrium, to which a non-chair conformation contributes. The same is true for methyl (methyl 2,3,4-tri-O-sulfonato-beta-D-glucopyranosid)uronate trisodium salt, methyl 2,3,4,6-tetra-O-sulfonato-beta-D-glucopyranoside tetrasodium salt, and octa-O-sulfonato-beta, beta-trehalose octasodium salt, with less obvious non-chair contributions. The effect is charge related. The conformational effect, which does not occur in analogous alpha-D-glucopyranoside derivatives, is discussed in terms of the anomeric effect.
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Affiliation(s)
- H P Wessel
- F. Hoffmann-La Roche Ltd, Pharma Division, Basel, Switzerland
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18
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19
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Jegge S, Lehmann J. Comparative stability of 1-alkoxyalkyl alpha-D-glucosides in the presence of acid or alpha-D-glucosidase from yeast. Carbohydr Res 1985; 142:47-59. [PMID: 3907829 DOI: 10.1016/s0008-6215(00)90732-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The aminated 1-alkoxyalkyl glycosides [(S)-2-amino-1-methoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (3) and [(R,S)-1-ethoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (4) have been synthesised and characterised. These compounds as well as [(R)-2-amino-1-methoxyethyl] alpha-D-glucopyranoside (1) prepared earlier are resistant against alpha-D-glucosidase (maltase, alpha-D-glucoside glucohydrolase, E.C. 3.2.1.20) from yeast, yet undergo hydrolysis under relatively mild acidic conditions. The kinetic parameters of the interaction with alpha-D-glucosidase and with acid were determined. The relative rates of acid hydrolysis of aminated 1-alkoxyalkyl glycosides compared with aminated ordinary glycosides suggest essential differences in the mechanism of acid-catalysed hydrolysis.
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20
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Chapter 11 Glycosyl transfer. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/s0167-7306(08)60382-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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22
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23
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Pal'yants NS, Abubakirov NK. Glycosylation of cardenolides. VI. Periplogenin mono- and diglucosiduronic acids. Chem Nat Compd 1977. [DOI: 10.1007/bf00566172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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25
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26
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27
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Triterpene glycosides of Ladyginia bucharica II. The structure of ladyginosides A and B. Chem Nat Compd 1972. [DOI: 10.1007/bf00563668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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28
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29
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31
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Batrakov SG, Pilipenko TV, Bergel'son LD. A diglyceride uronoside from streptomyces LA 7017. Chem Nat Compd 1970. [DOI: 10.1007/bf00565330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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32
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Heyns K, Chiemprasert T, Baltes W. Über nichtenzymatische Bräunungsreaktionen, VI. Über den Effekt ω-ständiger Substituenten aufN-Glykosid-Bildung und Amadori-Umlagerung beiD-Glucohexosen. ACTA ACUST UNITED AC 1970. [DOI: 10.1002/cber.19701030926] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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33
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Glycuronans. POLYSACCHARIDES 1970. [DOI: 10.1016/b978-0-08-013409-3.50015-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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34
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35
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36
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37
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38
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Painter EP, Kurihara NH. Substitution of acyclic sugar acetals. Is the acid-catalyzed substitution of erythro and threo l,2,3,4,5-penta-O-acetyl-l-arabinose S-ethyl monothioacetals anchimerically assisted? CAN J CHEM 1967. [DOI: 10.1139/v67-240] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rate constants for the inversion and for the 14C-acetoxy exchange of the diastereomeric 1,2,3,4,5-penta-O-acetyl S-ethyl monothioacetals show that the substitution is not anchimerically assisted by the C2-acetoxy group. The substitution of acyclic poly-O-acetyl sugar monoacetals is best explained by the formation of the acyclic intermediate [Formula: see text] (X = S or O) in the rate-determining step.
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39
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40
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Buncel E, Bradley PR. The acid-catalyzed hydrolysis of methyl 2-chloro-2-deoxy-β-D-glucopyranoside. CAN J CHEM 1967. [DOI: 10.1139/v67-087] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The kinetics of the hydrolysis of methyl 2-chloro-2-deoxy-β-D-glucopyranoside have been determined in hydrochloric acid solutions over a range of acid concentrations and temperatures. Chloro substitution reduces the rate by a factor of 35 compared with the hydroxy analogue. Application of the Hammett criterion indicates a unimolecular (A-1) mechanism of hydrolysis, as does application of the Bunnett criterion. The entropy of activation, however, is considerably smaller than that observed for the hydrolysis of methyl β-d-glucopyranoside. This is interpreted as being indicative of partial A-2 character.
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41
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42
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Zitko V, Bishop CT. FRACTIONATION OF PECTINS FROM SUNFLOWERS, SUGAR BEETS, APPLES, AND CITRUS FRUITS. CAN J CHEM 1965. [DOI: 10.1139/v65-447] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pectins from sunflower heads, sugar beet, apple, and citrus fruits were separated into acid-insoluble pectic acids and acid-soluble polysaccharides. The acid-soluble polysaccharides were shown by moving-boundary electrophoresis to be complex mixtures of four or five polysaccharides. The pectic acids were fractionated by precipitation with sodium acetate from aqueous solution. The fractions were examined for galacturonic acid content, specific rotation, limiting viscosity number, behavior on moving-boundary electrophoresis, and presence of neutral sugars. The results showed that each of the pectic acids contained two acidic components, one a galacturonan free of neutral sugars, the other a galacturonan to which neutral sugars were attached, probably as side chains.
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