- C3 Epimerization of Glucose, via Regioselective Oxidation and Reduction
-
Palladium-catalyzed oxidation can single out the secondary hydroxyl group at C3 in glucose, circumventing the more readily accessible hydroxyl at C6 and the more reactive anomeric hydroxyl. Oxidation followed by reduction results in either allose or allitol, each a rare sugar that is important in biotechnology. Also, N-acetylglucosamine is selectively oxidized at C3. These results demonstrate that glucose and N-acetylglucosamine, the most readily available chiral building blocks, can be versatile substrates in homogeneous catalysis.
- Jumde, Varsha R.,Eisink, Niek N. H. M.,Witte, Martin D.,Minnaard, Adriaan J.
-
-
Read Online
- Three new cycloartenol triterpenoid saponins from the roots of cimicifuga simplex wormsk
-
Three new cycloartenol triterpene saponins, named shengmaxinsides A-C, have been isolated from the ethyl acetate soluble fraction of an ethanol extract of Cimicifuga simplex Wormsk roots. Their structures were established by chemical tests and detailed spectroscopic analysis as 25-O-acetyl-7,8-didehydrocimigenol- 3-O-β-D-galactopyranoside (1), 7,8-didehydrocimigenol-3-O-β-D- galactopyranoside (2) and 7,8-didehydro-24S-Oacetylhydroshengmanol- 3-O-β-D-galactopyranoside (3), respectively.
- Kuang, Haixue,Su, Yang,Yang, Bingyou,Xia, Yonggang,Wang, Qiuhong,Wang, Zhibin,Yu, Zhengfan
-
-
Read Online
- Elucidating the effect of solid base on the hydrogenation of C5 and C6 sugars over Pt–Sn bimetallic catalyst at room temperature
-
Conversion of sugars into sugar alcohols at room temperature with exceedingly high yields are achieved over Pt–Sn/γ-Al2O3 catalyst in the presence of calcined hydrotalcite. pH of the reaction mixture significantly affects the conversion and selectivity for sugar alcohols. Selection of a suitable base is the key to achieve optimum yields. Various solid bases in combination with Pt–Sn/γ-Al2O3 catalysts were evaluated for hydrogenation of sugars. Amongst all combinations, the mixture (1:1 wt/wt) of Pt–Sn/γ-Al2O3 and calcined hydrotalcite showed the best results. Hydrotalcite helps to make the pH of reaction mixture alkaline at which sugar molecules undergo ring opening. The sugar molecule in open chain form has carbonyl group which can be polarized by Sn in Pt–Sn/γ-Al2O3 and Pt facilitates the hydrogenation. In the current work, effect of both; solid base and Sn as a promoter has been studied to improve the yields of sugar alcohols from various C5 and C6 sugars at very mild reaction conditions.
- Tathod, Anup P.,Dhepe, Paresh L.
-
-
- Selective and Scalable Synthesis of Sugar Alcohols by Homogeneous Asymmetric Hydrogenation of Unprotected Ketoses
-
Sugar alcohols are of great importance for the food industry and are promising building blocks for bio-based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H2, usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi-gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy.
- Tindall, Daniel J.,Mader, Steffen,Kindler, Alois,Rominger, Frank,Hashmi, A. Stephen K.,Schaub, Thomas
-
supporting information
p. 721 - 725
(2020/10/19)
-
- Structural features and antioxidant activity of a new galactoglucan from edible mushroom Pleurotus djamor
-
A new water soluble galactoglucan with apparent molecular weight ~1.61 × 105 Da, was isolated from the edible mushroom Pleurotus djamor by hot water extraction followed by purification through dialysis tubing cellulose membrane and sepharose 6B column chromatography. The sugar analysis showed the presence of glucose and galactose in a molar ratio of nearly 3:1 respectively. The structure of the repeating unit in the polysaccharide was determined through chemical and NMR experiments as:[Formula presented] In vitro antioxidant studies showed that the PDPS exhibited hydroxyl radical scavenging activity (EC50 = 1.681 ± 0.034 mg/mL), DPPH radical scavenging activity (EC50 = 3.83 ± 0.427 mg/mL), reducing power (EC50 = 4.258 ± 0.095 mg/mL), and ABTS radical quenching activity (EC50 = 0.816 ± 0.077 mg/mL). So, PDPS should be explored as a natural antioxidant.
- Maity, Gajendra Nath,Maity, Prasenjit,Khatua, Somanjana,Acharya, Krishnendu,Dalai, Sudipta,Mondal, Soumitra
-
p. 743 - 749
(2020/12/07)
-
- A novel low-molecular-mass pumpkin polysaccharide: Structural characterization, antioxidant activity, and hypoglycemic potential
-
The novel natural low-molecular-mass polysaccharide (SLWPP-3) from pumpkin (Cucurbia moschata) was separated from the waste supernatant after macromolecular polysaccharide production and purified using a DEAE cellulose-52 column and gel-filtration chromatography. Chemical and instrumental studies revealed that SLWPP-3 with a molecular mass of 3.5 kDa was composed of rhamnose, glucose, arabinose, galactose and uronic acid with a weight ratio of 1: 1: 4: 6: 15, and primarily contained →3,6)-β-D-Galp-(1→, →4)-α-GalpA-(1→(OMe), →4)-α-GalpA-(1→, →2,4)-α-D-Rhap-(1→, →3)-β-D-Galp-(1→, →4)-α-D-Glcp, and →4)-β-D-Galp residues in the backbone. The branch chain passes were connected to the main chain through the O-4 atom of glucose and O-3 atom of arabinose. Physiologically, the ability of SLWPP-3 to inhibit carbohydrate-digesting enzymes and DPPH and ABTS radicals, as well as protect pancreatic β cells from oxidative damage by decreasing MDA levels and increasing SOD activities, was confirmed. The findings elucidated the structural types of pumpkin polysaccharides and revealed a potential adjuvant natural product with hypoglycemic effects.
- Huang, Linlin,Li, Fei,Li, Quanhong,Liang, Li,Wei, Yunlu,Yu, Guoyong
-
-
- L-Xylo-3-hexulose, a new rare sugar produced by the action of acetic acid bacteria on galactitol, an exception to Bertrand Hudson's rule
-
Background: In acetic acid bacteria such as Gluconobacter oxydans or Gluconobacter cerinus, pyrroloquinoline quinone (PQQ) in the periplasm serves as the redox cofactor for several membrane-bound dehydrogenases that oxidize polyhydric alcohols to rare sugars, which can be used as a healthy alternative for traditional sugars and sweeteners. These oxidation reactions obey the generally accepted Bertrand Hudson's rule, in which only the polyhydric alcohols that possess cis D-erythro hydroxyl groups can be oxidized to 2-ketoses using PQQ as a cofactor, while the polyhydric alcohols excluding cis D-erythro hydroxyl groups ruled out oxidation by PQQ-dependent membrane-bound dehydrogenases. Methods: Membrane fractions of G. oxydans were prepared and used as a cell-free catalyst to oxidize galactitol, with or without PQQ as a cofactor. Results: In this study, we reported an interesting oxidation reaction that the polyhydric alcohols galactitol (dulcitol), which do not possess cis D-erythro hydroxyl groups, can be oxidized by PQQ-dependent membrane-bound dehydrogenase(s) of acetic acid bacteria at the C-3 and C-5 hydroxyl groups to produce rare sugars L-xylo-3-hexulose and D-tagatose. Conclusions: This reaction may represent an exception to Bertrand Hudson's rule. General significance: Bertrand Hudson's rule is a well-known theory in polyhydric alcohols oxidation by PQQ-dependent membrane-bound dehydrogenase in acetic acid bacteria. In this study, galactitol oxidation by a PQQ-dependent membrane-bound dehydrogenase represents an exception to the Bertrand Hudson's rule. Further identification of the associated enzymes and deciphering the explicit enzymatic mechanism will prove this theory.
- Xu, Yirong,Chi, Ping,Lv, Jiyang,Bilal, Muhammad,Cheng, Hairong
-
-
- Direct conversion of cellulose into isosorbide over Ni doped NbOPO4catalysts in water
-
Isosorbide is a versatile chemical intermediate for the production of a variety of drugs, chemicals, and polymers, and its efficient production from natural cellulose is of great significance. In this study, bifunctional catalysts based on niobium phosphates were prepared by a facile hydrothermal method and used for the direct conversion of cellulose to isosorbide under aqueous conditions. NH3-TPD analysis showed that a high acid content existed on the catalyst surface, and pyridine infrared spectroscopic analysis confirmed the presence of both Lewis acid and Br?nsted acid sites, both of which played an important role in the process of carbohydrate conversion. XRD and H2-TPR characterization determined the composition and the hydrogenation centers of the catalyst. An isosorbide yield of 47% could be obtained at 200 °C for 24 h under 3 MPa H2 pressure. The Ni/NbOPO4 bifunctional catalyst retains most of its activity after five consecutive runs with slightly decreased isosorbide yield of 44%. In addition, a possible reaction mechanism was proposed that the synergistic effect of surface acid sites and hydrogenation sites was favorable to enhancing the cascade dehydration and hydrogenation reactions during the conversion of cellulose to isosorbide. This study provides as an efficient strategy for the development of novel multifunctional heterogeneous catalysts for the one-pot valorisation of cellulose. This journal is
- Guo, Jiaxing,He, Minyao,Li, Cuiqing,Liu, ShanShan,Song, Yongji,Wang, Hong,Wang, Xincheng
-
supporting information
p. 10292 - 10299
(2020/07/14)
-
- Highly efficient catalytic conversion of cellulose into acetol over Ni-Sn supported on nanosilica and the mechanism study
-
Selective conversion of cellulose into high value-added C3 chemicals is a great challenge in biorefinery due to the complicated reaction process. In this work, 61.6% yield of acetol was obtained by one pot conversion of cellulose using Ni-Sn/SiO2 catalysts. A series of characterization methods including TEM, STEM-HAADF, EDS, AAS, XRD, XPS, H2-TPR, Py-FTIR, and CO2-TPD were carried out to explore the structure-activity relationship. The strong basicity of the catalysts was a key factor affecting the production of acetol. In addition, catalysts with the hydrothermally stable L-acid sites and no B-acid sites inhibited side reactions and ensured efficient conversion of cellulose into small molecules. Further studies showed that the formation of the Ni3Sn4 alloy significantly promoted the acetol production, and its weak hydrogenation activity inhibited further conversion of acetol. Noninteger valence tin species (Snδ+ and SnOx) were formed both in Ni3Sn4 and Sn/SiO2. These Sn species were the source of basic sites and the active sites for catalyzing cellulose to acetol. Under the synergistic catalysis of Sn/SiO2 and the Ni3Sn4 alloy, cellulose was efficiently converted into acetol. This work provides guidance for the selective conversion of cellulose into C3 products.
- Liu, Xiaohao,Liu, Xiaodong,Xu, Guangyue,Zhang, Ying,Wang, Chenguang,Lu, Qiang,Ma, Longlong
-
p. 5647 - 5656
(2019/11/05)
-
- Effect of Cu addition to carbon-supported Ru catalysts on hydrogenation of alginic acid into sugar alcohols
-
The objective of this study was to investigate the effect of Cu addition to carbon supported Ru catalysts on the hydrogenation of macroalgae-derived alginic acid into sugar alcohols, mainly sorbitol and mannitol. Both geometric and electronic effects were determined based on results of H2-TPR, H2- or CO-chemisorption, and XPS analyses after Cu was added to Ru. The addition of Cu to Ru caused blocking of active Ru surface and electron transfer between Ru and Cu. The intimate interaction between Ru and Cu formed RuCu bimetallic clusters which expedited hydrogen spillover from Ru to Cu. The highest yield of target sugar alcohols of 47.4% was obtained when 5 wt% of Ru and 1 wt% of Cu supported on nitric acid-treated activated carbon reacted at 180 °C for 2 h. The RuCu bimetallic catalyst exhibited deactivation upon repeated reactions due to the carbon deposition on the catalyst.
- Ban, Chunghyeon,Yang, Seungdo,Kim, Hyungjoo,Kim, Do Heui
-
-
- Synthesis method of partially methylated alditol acetate of monosaccharides
-
The invention discloses a synthesis method of partially methylated alditol acetate of monosaccharides, and belongs to the field of synthesis of partial methylation of the monosaccharides. The synthesis method comprises the following steps: (1) performing a reduction reaction on the monosaccharides to generate a corresponding alditol product; (2) performing a partial methylation reaction on the alditol product obtained through the reduction reaction; (3) performing an acetylation reaction on a product of the partial methylation reaction to obtain the partially methylated alditol acetate of the monosaccharides. Compared with an existing five-step synthesis method, the three-step synthesis method disclosed by the invention can simultaneously synthesize partially methylated alditol acetate compounds of furan and pyran type complete characteristics; meanwhile, the methylated reaction time is effectively shortened, so that hydroxyl groups are more rapidly methylated; compared with the same methylation time, the three-step synthesis method disclosed by the invention obviously improves a peak response value, and has the advantages of less synthesis steps, high strength, large quantity, high yield, simplicity and rapidness, and the like.
- -
-
Paragraph 0022; 0033-0034
(2019/10/10)
-
- Role of the Strong Lewis Base Sites on Glucose Hydrogenolysis
-
This work reports the individual role of strong Lewis base sites on catalytic conversion of glucose hydrogenolysis to acetol/lactic acid, including glucose isomerisation to fructose and pyruvaldehyde rearrangement/hydrogenation to acetol/lactic acid. Las
- Yazdani, Parviz,Wang, Bo,Gao, Feng,Kawi, Sibudjing,Borgna, Armando
-
p. 3845 - 3853
(2018/07/31)
-
- Hydrothermally Stable Ruthenium–Zirconium–Tungsten Catalyst for Cellulose Hydrogenolysis to Polyols
-
In this work, we describe a catalytic material based on a zirconium–tungsten oxide with ruthenium for the hydrogenolysis of microcrystalline cellulose under hydrothermal conditions. With these catalysts, polyols can be produced with high yields. High and stable polyol yields were also achieved in recycling tests. A catalyst with 4.5 wt % ruthenium in total achieved a carbon efficiency of almost 100 %. The prepared Zr-W oxide is mesoporous and largely stable under hydrothermal conditions (493 K and 65 bar hydrogen). Decomposition into the components ZrO2 and WO3 could be observed at temperatures of 1050 K in air.
- Lucas, Martin,Fabi?ovicová, Katarina,Claus, Peter
-
p. 612 - 618
(2017/12/28)
-
- METHOD FOR PRODUCING ISOPROPANOL BY CATALYTIC CONVERSION OF CELLULOSE
-
This invention provides a method for producing isopropanol from cellulose, which is characterized by: cellulose is catalytically converted to isopropanol under existence of a Cu-Cr catalyst. In the method, the Cu-Cr catalyst contains an active phase of CuCr2O4 or further contains an active phase selected from a group consisting of CuO and Cr2O3; the mass ratio of cellulose and water is 15 wt% or below; and the temperature of catalytic reaction is 200-270℃.
- -
-
Page/Page column 14
(2017/07/13)
-
- Influence of the Surface Chemistry of Multiwalled Carbon Nanotubes on the Selective Conversion of Cellulose into Sorbitol
-
Carbon nanotubes (CNT) were submitted to liquid-phase chemical treatments using HNO3 and subsequently to gas-phase thermal treatments to incorporate different sets of oxygenated groups on the surface. The modified CNT were used as supports for 0.4 wt % Ru in the direct conversion of ball-milled cellulose to sorbitol and high conversions were reached after 3 h at 205 °C. Ru supported on the original CNT, although less active, was the most selective catalyst for the one-pot process (70 % sorbitol selectivity after 2 h). Unlike the one-pot process, the support acidity greatly promoted the rate of cellulose hydrolysis (35 % increase after 2 h) and the glucose selectivity (12 % increase after 2 h). The rate of glucose hydrogenation was almost not affected by the support modification. However, the catalyst acidity improved the sorbitol selectivity from glucose. The support acidity was a central factor for the one-pot conversion of cellulose, as well as for the individual hydrolysis and hydrogenation steps, and the original CNT supported Ru catalyst was the most efficient and selective catalyst for the direct conversion of cellulose to sorbitol.
- Ribeiro, Lucília S.,Delgado, Juan J.,de Melo órf?o, José J.,Ribeiro Pereira, M. Fernando
-
p. 888 - 896
(2017/03/13)
-
- Discovery and characterization of family 39 glycoside hydrolases from rumen anaerobic fungi with polyspecific activity on rare arabinosyl substrates
-
Enzyme activities that improve digestion of recalcitrant plant cell wall polysaccharides may offer solutions for sustainable industries. To this end, anaerobic fungi in the rumen have been identified as a promising source of novel carbohydrate active enzymes (CAZymes) that modify plant cell wall polysaccharides and other complex glycans. Many CAZymes share insufficient sequence identity to characterized proteins from other microbial ecosystems to infer their function; thus presenting challenges to their identification. In this study, four rumen fungal genes (nf2152, nf2215, nf2523, and pr2455) were identified that encode family 39 glycoside hydrolases (GH39s), and have conserved structural features with GH51s. Two recombinant proteins, NF2152 and NF2523, were characterized using a variety of biochemical and structural techniques, and were determined to have distinct catalytic activities. NF2152 releases a single product, β1,2-arabinobiose (Ara2) from sugar beet arabinan (SBA), and β1,2-Ara2 and α-1,2-galactoarabinose (Gal-Ara) from rye arabinoxylan (RAX). NF2523 exclusively releases α-1,2-Gal-Ara from RAX, which represents the first description of a galacto-(-1,2)-arabinosidase. Both β-1,2-Ara2 and α-1,2-Gal-Ara are disaccharides not previously described within SBA and RAX. In this regard, the enzymes studied here may represent valuable new biocatalytic tools for investigating the structures of rare arabinosyl-containing glycans, and potentially for facilitating their modification in industrial applications.
- Jones, Darryl R.,Uddin, Muhammed Salah,Gruninger, Robert J.,Pham, Thi Thanh My,Thomas, Dallas,Boraston, Alisdair B.,Briggs, Jonathan,Pluvinage, Benjamin,McAllister, Tim A.,Forster, Robert J.,Tsang, Adrian,Selinger, L. Brent,Abbott, D. Wade
-
p. 12606 - 12620
(2017/08/02)
-
- Selective C?O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by Piers’ Borane Generated In Situ
-
Described herein is the selective reduction of sugars with hydrosilanes catalyzed by using Piers’ borane [(C6F5)2BH] generated in situ. The hydrosilylative C?O bond cleavage of silyl-protected mono- and disaccharides in the presence of a (C6F5)2BH catalyst, generated in situ from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. A study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.
- Zhang, Jianbo,Park, Sehoon,Chang, Sukbok
-
supporting information
p. 13757 - 13761
(2017/10/09)
-
- Unravelling the Ru-Catalyzed Hydrogenolysis of Biomass-Based Polyols under Neutral and Acidic Conditions
-
The aqueous Ru/C-catalyzed hydrogenolysis of biomass-based polyols such as erythritol, xylitol, sorbitol, and cellobitol is studied under neutral and acidic conditions. For the first time, the complete product spectrum of C2-C6 polyols is identified and, based on a thorough analysis of the reaction mixtures, a comprehensive reaction mechanism is proposed, which consists of (de)hydrogenation, epimerization, decarbonylation, and deoxygenation reactions. The data reveal that the Ru-catalyzed deoxygenation reaction is highly selective for the cleavage of terminal hydroxyl groups. Changing from neutral to acidic conditions suppresses decarbonylation, consequently increasing the selectivity towards deoxygenation.
- Hausoul, Peter J. C.,Negahdar, Leila,Schute, Kai,Palkovits, Regina
-
p. 3323 - 3330
(2015/10/19)
-
- Directed divergent evolution of a thermostable D-tagatose epimerase towards improved activity for two hexose substrates
-
Functional promiscuity of enzymes can often be harnessed as the starting point for the directed evolution of novel biocatalysts. Here we describe the divergent morphing of an engineered thermostable variant (Var8) of a promiscuous D-tagatose epimerase (DTE) into two efficient catalysts for the C3 epimerization of d-fructose to d-psicose and of L-sorbose to L-tagatose. Iterative single-site randomization and screening of 48 residues in the first and second shells around the substratebinding site of Var8 yielded the eight-site mutant IDF8 (nine-fold improved kcat for the epimerization of D-fructose) and the six-site mutant ILS6 (14-fold improved epimerization of L-sorbose), compared to Var8. Structure analysis of IDF8 revealed a charged patch at the entrance of its active site; this presumably facilitates entry of the polar substrate. The improvement in catalytic activity of variant ILS6 is thought to relate to subtle changes in the hydration of the bound substrate. The structures can now be used to select additional sites for further directed evolution of the ketohexose epimerase.
- Bosshart, Andreas,Hee, Chee Seng,Bechtold, Matthias,Schirmer, Tilman,Panke, Sven
-
p. 592 - 601
(2015/04/13)
-
- One-pot catalytic conversion of cellulose into polyols with Pt/CNTs catalysts
-
A series of Pt nanoparticles supported on carbon nanotubes (CNTs) were synthesized using the incipient-wetness impregnation method. These catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM) techniques. The characterization results indicate that the Pt nanoparticles were highly dispersed on the surface of the CNTs, and the mean size was less than 5 nm. These catalysts were utilized to convert cellulose to hexitol, ethylene glycerol (EG), and 1,2-propylene glycol (1,2-PG) under low H2 pressure. The total yields were as high as 71.4% for EG and 1,2-PG using 1 Pt/CNTs as the catalyst in the hydrolytic hydrogenation of cellulose under mild reaction conditions.
- Yang, Li,Yan, Xiaopei,Wang, Qiwu,Wang, Qiong,Xia, Haian
-
supporting information
p. 87 - 92
(2015/03/05)
-
- Arabinogalactan hydrolysis and hydrolytic hydrogenation using functionalized carbon materials
-
Hydrolysis of the hemicellulose arabinogalactan was studied in this work over several functionalized carbon materials, which were specifically treated to increase their acidities. Hydrolytic hydrogenation of arabinogalactan was investigated using the same materials in a mechanical mixture with ruthenium supported on active carbon. Application of these mixtures resulted in formation of polyols, suppressing simultaneously the generation of side products hydroxymethylfurfural (HMF) and furfural. Formation of high molecular weight compounds (aggregates of sugars and humins) was still quite substantial with a mechanical mixture of Ru/C and a carbon material prepared from sucrose by activation with zinc chloride to increase porosity. Post-treatment of this carbonaceous material with sulphuric acid significantly influenced kinetics of high molecular weight products formation resulting also in elevation of sugar alcohols yields.
- Murzin, D.Yu.,Murzina,Tokarev,Shcherban,W?rn?,Salmi
-
p. 169 - 176
(2015/02/19)
-
- One-pot conversions of raffinose into furfural derivatives and sugar alcohols by using heterogeneous catalysts
-
Inedible and/or waste biomass reserves are being strongly focused upon as a suitable new energy and chemical source. Raffinose, which is an indigestible trisaccharide composed of glucose, galactose, and fructose, is found abundantly in beet molasses, sugar cane, and seeds of many leguminous plants. Herein, we demonstrate the one-pot synthesis of furan derivatives and sugar alcohols from raffinose by using heterogeneous acid, base, and/or metal-supported catalysts. The combination of Amberlyst-15 and hydrotalcite (HT) showed a high activity (37% yield) for 5-hydroxymethyl-2-furaldehyde (HMF) through continuous hydrolysis, isomerization, and dehydration reactions. In addition, the use of a hydrotalcite-supported ruthenium catalyst (Ru/HT) successfully afforded 2,5-diformylfuran (DFF, 27% yield) from HMF produced by raffinose, directly. Moreover, the hydrogenation of hexoses obtained by raffinose hydrolysis into sugar alcohols (galactitol, mannitol, sorbitol) was also achieved in a high yield (91 %) with Amberlyst-15 and Ru/HT catalysts. Thus, we suggest that raffinose has great potential for the synthesis of important industrial intermediates under mild reaction conditions.
- Dabral, Saumya,Nishimura, Shun,Ebitani, Kohki
-
p. 260 - 267
(2014/03/21)
-
- Aqueous phase hydrogenolysis of glucose to 1,2-propanediol over copper catalysts supported by sulfated spherical carbon
-
Aqueous phase hydrogenolysis of glucose was carried out over copper catalysts supported by sulfated spherical carbon for selective production of 1,2-propanediol. The sulfated carbon shows higher acidity by sulfation of its resin precursor than unsulfated or commercial ones. By changing copper loading, the hydrogenolysis capability and the acidity of catalysts were modified to suitable extents, which can optimize the selectivity to 1,2-propanediol. At a moderate copper loading, 5.0Cu/s-AC catalyst has the highest yield of 1,2-propanediol. This catalyst has a lifetime of over 300 h. However, its stability is required to be further improved.
- Liang, Dong,Liu, Chengwei,Deng, Shuping,Zhu, Yulei,Lv, Chunxiang
-
p. 108 - 113
(2014/07/08)
-
- Water-soluble polysaccharides from finger citron fruits (Citrus medica L. var. sarcodactylis)
-
Four water-soluble polysaccharides, FCp-1, FCp-2, FCp-3, and FCp-4 were obtained from finger citron fruits (Citrus medica L. var. sarcodactylis) by hot-water extraction and ethanol precipitation, followed by routine separation procedure. Based on the calibration curve, molecular weights of them were estimated to be 113.9, 32.6, 140.3, and 177.1 kDa respectively. The acid hydrolysis, methylation, IR, GC-MS, and NMR experiments were used for composition analysis. FCp-1 was a heteropolysaccharide composed of arabinose, galactose, glucose, rhamnose, and xylose, with a molar ratio of 3.0:7.0:4.1:1.0:1.5. FCp-2 and FCp-4 were →4)-α-d-GalpA(1→ linking galacturonan differ in molecular weights. FCp-3 was a →6)-α-d-Glcp(1→ linking glucan. According to the results of in vitro assays, FCp-3 showed significantly and moderately enhancing capacities toward the proliferation of splenocytes and thymocytes respectively. Thus, FCp-3 or analogs may have further use as immunomodulatory agents.
- He, Zhengchun,Liang, Fengjie,Zhang, Yuyang,Pan, Yuanjiang
-
p. 100 - 104
(2014/04/03)
-
- Conversion of sugars to ethylene glycol with nickel tungsten carbide in a fed-batch reactor: High productivity and reaction network elucidation
-
Bifunctional nickel tungsten carbide catalysis was used for the conversion of aqueous sugar solutions into short-chain polyols such as ethylene glycol. It is shown that very concentrated sugar solutions, viz. up to 0.2 kg L -1, can be converted without loss of ethylene glycol selectivity by gradually feeding the sugar solution. Detailed investigation of the reaction network shows that, under the applied reaction conditions, glucose is converted via a retro-aldol reaction into glycol aldehyde, which is further transformed into ethylene glycol by hydrogenation. The main byproducts are sorbitol, erythritol, glycerol and 1,2-propanediol. They are formed through a series of unwanted side reactions including hydrogenation, isomerisation, hydrogenolysis and dehydration. Hydrogenolysis of sorbitol is only a minor source of ethylene glycol. To assess the relevance of the fed-batch system in biomass conversions, both the influence of the catalyst composition and the reactor setup parameters like temperature, pressure and glucose addition rate were optimized, culminating in ethylene glycol yields up to 66% and separately, volume productivities of nearly 300 gEG L-1 h-1.
- Ooms, Roselinde,Dusselier, Michiel,Geboers, Jan A.,Op De Beeck, Beau,Verhaeven, Rick,Gobechiya, Elena,Martens, Johan A.,Redl, Andreas,Sels, Bert F.
-
p. 695 - 707
(2014/02/14)
-
- New 9,19-cycloartenol glycosides isolated from the roots of Cimicifuga simplex and their anti-inflammatory effects
-
Two new cycloartenol triterpene saponins, 3β,16α-dihydroxy-12-acetoxy-16,22-cyclo-23-ketone-24R,25-epoxy-cycloartane-3-O-β-d-galactopyranoside (1), 3β,16α-dihydroxy-12-acetoxy-16,22-cyclo-23-ketone-24R,25-epoxy-cycloartane-7-ene-3-O-β-d-xylopyranoside (2), were isolated from the ethyl acetate soluble fraction of the roots of Cimicifuga simplex Wormsk. Their structures were established by detailed spectroscopic analysis, including extensive 2D NMR data. Their anti-proinflammatory activities were also carried out by LPS-stimulated IL-6, IL-23 and TNF-α genes expression in RAW cells in vitro using Q-PCR method.
- Su, Yang,Wu, Lun,Wang, Qiuhong,Yang, Bingyou,Kuang, Haixue
-
supporting information
p. 5688 - 5691
(2015/01/08)
-
- Promoting effect of SnOx on selective conversion of cellulose to polyols over bimetallic Pt-SnOx/Al2O3 catalysts
-
Cellulose is the most abundant source of biomass in nature, and its selective conversion into polyols provides a viable route towards the sustainable synthesis of fuels and chemicals. Here, we report the marked change in the distribution of polyols in the cellulose reaction with the Sn/Pt atomic ratios in a wide range of 0.1-3.8 on the SnOx-modified Pt/Al 2O3 catalysts. Such a change was found to be closely related to the effects of the Sn/Pt ratios on the activity for the hydrogenation of glucose and other C6 sugar intermediates involved in the cellulose reaction as well as to the notable activity of the segregated SnO x species for the selective degradation of the sugar intermediates on the Pt-SnOx/Al2O3 catalysts. At lower Sn/Pt ratios of 0.1-1.0, there existed electron transfer from the SnOx species to the Pt sites and strong interaction between the catalysts, as characterized by temperature-programmed reduction in H2 and infrared spectroscopy for CO adsorption, which led to their superior hydrogenation activity (per exposed Pt atom), and in-parallel higher selectivity to hexitols (e.g. sorbitol) in the cellulose reaction, as compared to Pt/Al 2O3. The hexitol selectivity reached the greatest value of 82.7% at the Sn/Pt ratio of 0.5, nearly two times that of Pt/Al 2O3 at similar cellulose conversions (～20%). As the Sn/Pt ratios exceeded 1.5, the Pt-SnOx/Al2O3 catalysts exhibited inferior hydrogenation activity (per exposed Pt atom), due to the formation of the crystalline Pt-Sn alloy, which led to the preferential conversion of cellulose to C2 and especially C3 products (e.g. acetol) over hexitols, most likely involving the isomerization of glucose to fructose and retro-aldol condensation of these sugars on the segregated SnOx species, apparently in the form of Sn(OH)2. These findings clearly demonstrate the feasibility for rational control of the cellulose conversion into the target polyols (e.g. acetol or propylene glycol), for example, by the design of efficient catalysts based on the catalytic functions of the SnOx species with tunable hydrogenation activity.
- Deng, Tianyin,Liu, Haichao
-
p. 116 - 124
(2013/02/26)
-
- Substrate binding to Candida tenuis xylose reductase during catalysis
-
Candida tenuis xylose reductase (CtXR) is studied by in situ NMR, saturation transfer difference (STD) NMR, and molecular docking with respect to its substrate and coenzyme binding in ternary complexes. The natural substrate Xyl as well as Glc and methyl-glucosides preferentially bind as α-anomers of the pyranose forms. These α-anomers are transformed faster, predominately leading to STD effects in the formed products, and can be better docked into the CtXR active site than the β-anomer. The reduction is initiated by α-Xylp ring opening prior to hydride transfer from NADH. Binding and transformation of unnatural 2,4-dichloroacetophenone is not as good, although it is reduced with very high catalytic efficiency. STD NMR indicates a reasonable amount to leave the ternary complex in unreduced form. The molecular docking calculation confirms this result, as only a couple of the investigated ternary complexes allow reduction of the substrates.
- Vogl, Michael,Brecker, Lothar
-
p. 25997 - 26004
(2013/12/04)
-
- Copper-based catalysts for efficient valorization of cellulose
-
Noble causes: Cellulose is effectively converted into methanol, propylene, and ethylene glycol over Cu-based catalysts. Overall yields of above 93 %, together with 63 % yield of C1-C3 compounds, can be reached over simple noble-metal
- Tajvidi, Kameh,Pupovac, Kristina,Kuekrek, Murhat,Palkovits, Regina
-
p. 2139 - 2142
(2013/01/15)
-
- Selective conversion of microcrystalline cellulose into hexitols on nickel particles encapsulated within ZSM-5 zeolite
-
A highly active and selective Ni/ZSM-5 catalyst was prepared by a simple method. A selectivity of 91.2% to hexitols was obtained at intermediate conversion in the hydrolytic hydrogenation of cellulose.
- Liang, Guanfeng,Cheng, Haiyang,Li, Wei,He, Limin,Yu, Yancun,Zhao, Fengyu
-
supporting information; experimental part
p. 2146 - 2149
(2012/09/10)
-
- Hydrolytic hydrogenation of hemicellulose over metal modified mesoporous catalyst
-
The hydrolytic hydrogenation of hemicellulose arabinogalactan, into sugars, sugar alcohols and furfurals was carried out in a batch reactor using modified mesoporous MCM-48 material incorporated with ruthenium metal into the framework. The bi-functional catalytic materials, MCM-48 and Ru-MCM-48 were synthesized, characterized and investigated in the title reaction at total pressure of 20 bar hydrogen, using an initial arabinogalactan concentration of 0.4 wt%, at 458 K. The transformation of the hemicellulose consists of arabinogalactan hydrolysis to the monosaccharides, l-arabinose and d-galactose followed by the subsequent hydrogenation to sugar alcohols, arabitol and galactitol or dehydration of the monomers to furfural and 5-hydroxymethylfurfural. The yields of the main products, i.e. sugars, sugar alcohols and furfurals were varied depending on the strength of the acid sites and the presence of metal in the structure of the ruthenium modified catalyst. Ru-MCM-48 displayed high catalytic activity and the sugar alcohols were obtained selectively from the hemicellulose. The catalytic performance of the mesoporous MCM-48 catalysts with respect to the catalyst structure, acidity and presence of the metal was evaluated.
- Kusema, Bright T.,Faba, Laura,Kumar, Narendra,M?ki-Arvela, P?ivi,Díaz, Eva,Ordó?ez, Salvador,Salmi, Tapio,Murzin, Dmitry Yu.
-
-
- METHOD FOR PRODUCING ETHYLENE GLYCOL FROM POLYHYDROXY COMPOUND
-
A method for producing ethylene glycol, including (a) adding a polyhydroxy compound and water to a sealed high-pressure reactor, (b) removing air and introducing hydrogen, and (c) allowing the polyhydroxy compound to react in the presence of a catalyst while stiffing. The catalyst includes a first active ingredient and a second active ingredient. The first active ingredient includes a transition metal of Group 8, 9, or 10 selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, and platinum, and/or a mixture thereof. The second active ingredient includes a metallic state of molybdenum and/or tungsten, or a carbide, nitride, or phosphide thereof. The method is carried out at a hydrogen pressure of 1-12 MPa, at a temperature of 120-300° C. for not less than 5 min in a one-step catalytic reaction. The efficiency, selectivity, and the yield of ethylene glycol are high. The preparation process is simple and the materials used are renewable.
- -
-
Page/Page column 3; 5
(2011/04/14)
-
- Heteropoly acids as efficient acid catalysts in the one-step conversion of cellulose to sugar alcohols
-
Cellulose and even spruce can be converted efficiently into valuable platform chemicals via combined hydrolysis and hydrogenation in the aqueous phase. Thereby, heteropoly acids together with supported ruthenium catalysts show not only high activity but also remarkable selectivity to sugar alcohols reaching up to 81% yield of C4 to C6 sugar alcohols in only 7 h at 160 °C.
- Palkovits, Regina,Tajvidi, Kameh,Ruppert, Agnieszka M.,Procelewska, Joanna
-
supporting information; experimental part
p. 576 - 578
(2011/03/17)
-
- Extraction, purification, characterization and hypoglycemic activity of a polysaccharide isolated from the root of Ophiopogon japonicus
-
In this research, a water-soluble polysaccharide (OJP1) extracted with hot water from the roots of Ophiopogon japonicus which is a traditional Chinese medicinal herb was precipitated with 95% ethanol and purified by DEAE-52 cellulose anion-exchange and Sephadex G-100 gel filtration chromatography. The high performance gel permeation chromatography (HPGPC) analysis showed that the average molecular weight (Mw) of OJP1 was 35.2 kDa. Monosaccharides analysis revealed that the OJP1 is composed of Ara, Glc, Gal with a relative molar ratio of 1:16:8. Pharmaceutical experiments showed OJP1 can significantly reduce blood glucose level, increase the insulin level and remediating destruction of pancreatic islets in STZ-induced diabetic rats compared with the diabetic control group. The study shows that OJP1 has an anti-diabetic effect on STZ-induced diabetic rats, and has potential use as an anti-diabetic agent. Copyright
- Chen, Xiaoming,Jin, Jing,Tang, Jia,Wang, Zhongfu,Wang, Junjun,Jin, Liqin,Lu, Jianxin
-
experimental part
p. 749 - 754
(2011/06/27)
-
- Amino acid catalyzed neogenesis of carbohydrates: A plausible ancient transformation
-
Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with > 99% ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic "gluconeogenesis" may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with > 99% ee. In addition, the direct amino acid catalyzed C2+C 2+C2 methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.
- Cordova, Armando,Ibrahem, Ismail,Casas, Jesus,Sunden, Henrik,Engqvist, Magnus,Reyes, Efraim
-
p. 4772 - 4784
(2007/10/03)
-
- METHOD FOR PREPARING SUGAR ALCOHOLS BY CATALYTIC HYDROGENATION OF SUGARS
-
Disclosed a method of producing sugar alcohols through the hydrogenation of sugars using a catalyst in which ruthenium is supported on a carrier comprising silica, zirconia, or a mixture thereof. The method includes hydrogenating sugar under relatively moderate reaction conditions using a catalyst in which ruthenium is supported on a carrier including silica, zirconia, or a mixture thereof, with the metal dispersion of 10% or more, and in which the chlorine content is less than 100ppm. Sugar alcohol is produced through a continuous process under moderate conditions of low temperature and pressure at a high yield, thereby generating few by products or wastes and producing sugar alcohol without a complicated separation process.
- -
-
Page/Page column 13-14
(2008/06/13)
-
- METHOD OF DESALTING SUGAR SOLUTION AND ANION EXCHANGER
-
The present invention provides the means for suppressing the production of decomposition reactant, isomerization reactant, colored material, and so on when a saccharide solution is desalted, thereby suppressing the production of impurities and preventing coloration of an ion exchange resin and decrease in the desalting capacity of the ion exchange resin. The desalting of a saccharide solution is performed by using an anion exchange resin supporting a carbonate ion and/or a hydrogencarbonate ion.
- -
-
-
- METHOD FOR PRODUCING SUGAR ALCOHOL
-
A process for producing sugar alcohols having six carbon atoms, which comprises hydrogenating ketohexose, such as psicose, tagatose, sorbose and the like, in the presence of a catalyst containing a metal selected from the elements belonging to the eighth family in the periodic table, such as nickel, ruthenium, platinum, palladium and the like, is provided. According to this process, sugar alcohols having six carbon atoms can be produced efficiently at a large amount, the separation and recovering of the catalyst after completing the reaction are facilitated, and sugar alcohols having a desired production ratio can be produced efficiently.
- -
-
-
- Multiple Forms of Xylose Reductase in Candida intermedia: Comparison of Their Functional Properties Using Quantitative Structure-Activity Relationships, Steady-State Kinetic Analysis, and pH Studies
-
The xylose-fermenting yeast Candida intermedia produces two isoforms of xylose reductase: one is NADPH-dependent (monospecific xylose reductase; msXR), and another is shown here to prefer NADH ≈4-fold over NADPH (dual specific xylose reductase; dsXR). To compare the functional properties of the isozymes, a steady-state kinetic analysis for the reaction D-xylose + NAD(P)H + H + ? xylitol + NAD(P)+ was carried out and specificity constants (kcat/Kaldehyde) were measured for the reduction of a series of aldehydes differing in side-chain size as well as hydrogen-bonding capabilities with the substrate binding pocket of the enzyme. dsXR binds NAD(P)+ (KiNAD+ = 70 μM; KiNADP+ = 55 μM) weakly and NADH (Ki = 8 μM) about as tightly as NADPH (Ki = 14 μM). msXR shows uniform binding of NADPH and NADP + (KiNADP+ ≈ KiNADPH = 20 μM). A quantitative structure-activity relationship analysis was carried out by correlating logarithmic kcat/Kaldehyde values for dsXR with corresponding logarithmic kcat/Kaldehyde values for msXR. This correlation is linear with a slope of ≈1 (r2 = 0.912), indicating that no isozyme-related pattern of substrate specificity prevails and aldehyde-binding modes are identical in both XR forms. Binary complexes of dsXR-NADH and msXR-NADPH show the same macroscopic pK of ≈9.0-9.5, above which the activity is lost in both enzymes. A lower pK of 7.4 is seen for dsXR-NADPH. Specificity for NADH and greater binding affinity for NAD(P)H than NAD(P)+ are thus the main features of enzymic function that distinguish dsXR from msXR.
- Nidetzky, Bernd,Brueggler, Kaspar,Kratzer, Regina,Mayr, Peter
-
p. 7930 - 7935
(2007/10/03)
-
- Water-soluble constituents of caraway: aromatic compound, aromatic compound glucoside and glucides.
-
From the water-soluble portion of the methanolic extract of caraway (fruit of Carum carvi L.), an aromatic compound, an aromatic compound glucoside and a glucide were isolated together with 16 known compounds. Their structures were clarified as 2-methoxy-2-(4'-hydroxyphenyl)ethanol, junipediol A 2-O-beta-D-glucopyranoside and L-fucitol, respectively.
- Matsumura, Tetsuko,Ishikawa, Toru,Kitajima, Junichi
-
p. 455 - 459
(2007/10/03)
-
- Use of alkylated iminosugars to treat multidrug resistance
-
Methods and compositions for preventing, reducing, or reversing multidrug resistance (MDR) during cancer chemotherapy in patients undergoing treatment with therapeutically effective amounts of chemotherapeutic agents are provided. The methods comprise administering an anti-MDR effective amount of an N-substituted-1,5-dideoxy-1,5-imino-D-glucitol or galactitol iminosugar to a patient.
- -
-
-
- Aldol Addition of Lithium and Boron Enolates of 1,3-Dioxan-5-ones to Aldehydes. A New Entry into Monosaccharide Derivatives
-
Methods allowing control of stereoselectivity in aldol reactions of enolates derived from 1,3-dioxan-5-ones (4) are described. Boron enolates, generated in situ, react with benzaldehyde to give the corresponding anti aldol selectively (the anti:syn ratio of up to 96:4) in high yield. Lithium enolates give high anti selectivity only with aldehydes branched at the α-position. Enantioselective deprotonation of CS symmetrical dioxanones (e.g., 4b) can be accomplished efficiently, with enantiomeric excess of up to 90%, with chiral lithium amide bases of general structure PhCH-(Me)N(Li)R (9, 10) if the R group is sufficiently bulky (e.g, R = adamantyl) or is fluorinated (e.g., R = CH2CF3). Dioxanone boron and lithium enolates react readily with glyceraldehyde derivatives (19), yielding protected ketohexoses (20 and 21).
- Majewski, Marek,Nowak, Pawel
-
p. 5152 - 5160
(2007/10/03)
-
- Enantiomerically Pure, Highly Functionalized Tetrahydrofurans from Simple Carbohydrate Precursors
-
6-Bromo-6-deoxy-1,4-aldonolactones and 6-bromo-6-deoxy-alditols with D-galacto, D-altro-, D-manno- and D-ido-configuration were selectively converted into hydroxylated tetrahydrofuran derivatives by simple heating in water.The 6-bromo-6-deoxy-altritol (10) and 6-bromo-6-deoxy-D-iditol (25) reacted even at room temperature.Likewise, 6-bromo-2,6-dideoxy-aldonolactones with D-arabino- (29) and D-lyxo-configuration (31) gave the corresponding 2-deoxy-3,6-anhydride, when heated in water.The rate of formation of the furan ring by intramolecular nucleophilic substitution was determined by the conformation of the bromopolyols in water.
- Lundt, Inge,Frank, Holger
-
p. 13285 - 13298
(2007/10/02)
-
- Total synthesis of the L-hexoses
-
Enantiomerically pure polyhydroxylated natural products are synthesized by using a reiterative two-carbon extension cycle consisting of four key transformations. The generality and efficiency of this methodology are demonstrated in the total synthesis of all eight L-hexoses.
- Ko, Soo Y.,Lee, Albert W. M.,Masamune, Satoru,Reed III, Lawrence A.,Sharpless, K. Barry,Walker, Frederick J.
-
p. 245 - 264
(2007/10/02)
-
- Interglucosyl Attack of Hydroxyl Group to Epoxy Ring of 2A,3A-Anhydro-(2AS)-α-cyclodextrin. Selective Preparation of 3A,2B-Anhydro-α-cyclodextrin
-
2A,3A-Anhydro-(2AS)-α-cyclodextrin was isomerized exclusively to 3A,2B-anhydro-α-cyclodextrin by the reaction with aqueous alkali.This implies the selective and interglucosyl attack of 3F-OH to the epoxy ring.
- Fujita, Kahee,Tahara, Tsutomu,Sasaki, Hideaki,Egashira, Yoshimitsu,Shingu, Tetsuro,et al.
-
p. 917 - 920
(2007/10/02)
-
- Analysis of Aldoses and Alditols by Capillary Gas Chromatography as Alditol Trifluoroacetates
-
Analysis of aldoses and alditols by capillary gas chromatography as alditol trifluoroacetates was carried out by using a fused silica capillary column (cyanopropyl-bonded phase) and a hydrogen flame ionization detector.Seventeen alditols were completely resolved within 18 min.The detection limits were about 1-4 ng/injection which are one hundred times smaller than as those of a packed column.Special care was necessary in the use of internal standards for the simultaneous determination of multiple components, and good reproducibility was obtained by using double internal standards.Keywords- aldose; alditol; alditol trifluoroacetate; capillary gas chromatography
- Haga, Hidehiko,Nakajima, Terumi
-
p. 1562 - 1564
(2007/10/02)
-
- Nitrosation of 2-Amino-2-deoxy-D-galactitol; a Model Experiment for the Study of Reduced Oligosaccharides derived from Mucus Glycoproteins
-
Sequential nitrosation, and reduction with sodium cyanoborohydride, of 2-amino-2-deoxy-D-galactitol gave, as major products, 2-deoxy-D-lyxo- (and/or -xylo-)hexitol (39percent) and glycerol (43percent).Minor products included a hexitol and diastereoisomeric 2-deoxy-2-hydroxymethyl-D-pentitols (provisionally identified).Reduction of the nitrosation products with sodium borodeuteride gave 2-deoxy-D-hexitols with more deuterium at C-3 than at C-1.Glycerol was also shown to be a product of the nitrosation and reduction of 2-amino-2-deoxy-D-glucitol.The implications of these results for the nitrosation of the 2-amino-2-deoxy-D-galactitol-containing oligosaccharides derived from mucus glycoproteins are discussed.
- Carter, Steven R.,Williams, J. Michael,Clamp, John R.
-
p. 2775 - 2778
(2007/10/02)
-
- SYNTHESIS OF PHOSPHATIDYL-β-GLUCOSYL GLYCEROL CONTAINING A DIOLEOLYL DIGLYCERIDE MOIETY. APPLICATION OF THE TETRAISOPROPYLDISILOXANE-1,3-DIYL (TIPS) PROTECTING GROUP IN SUGAR CHEMISTRY. PART IV
-
The preparation of phosphatidyl-β-glucosyl diglyceride 12c is described.The synthesis of glycophospholipid 12c was accomplished by using: (a) the levulinoyl group for the temporary protection of the glucose hydroxyl functions of 6b, which could then be converted into the dioleoyl substituted derivative 7c; (b) the tetraisopropyldisiloxane-1,3-diyl (TIPS) group to protect the 3'- and 4'-hydroxyl groups of 7c, in a two step procedure, to afford compound 8; (c) a 2,4-dichlorophenyl protected phosphatidic acid derivative 11.Compound 11 could be selectively coupled to the primary hydroxyl function of 8 to afford the fully protected glycophospholipid 12a.Finally, removal of the 2,4-dichlorophenyl and TIPS protecting groups from 12a was performed with syn-4-nitrobenzaldoximate and fluoride ions, respectively, to afford glycophospholipid 12c.
- Boeckel, C. A. A. van,Visser, G. M.,Boom, J. H. van
-
p. 4557 - 4566
(2007/10/02)
-
