- ESIMS and NMR studies on the selective deprotection of acetylated glucosides by dibutyltin oxide
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The reaction process for the selective deprotection of acetylated glucosides by dibutyltin oxide in methanol is investigated by using methyl 2,3,4,6-tetra-O-acetyl-α-d-glucopyranoside as a model substrate with ESIMS and NMR techniques. According to the results, it is inferred that at first, dimeric 1,3-dimethoxytetrabutyldistannoxane is formed by the reaction of dibutyltin oxide with methanol, and then the tetraorganodistannoxane reacts with the acetylated glucoside to produce glucoside-organotin complex intermediates. Finally, the complex intermediates are hydrolyzed leading to the free-OH glucoside and organotin acetate derivatives. The reaction is affected by neighboring group participation and steric hindrance, which allow for high selectivities among different acetyl groups in acetylated glucosides.
- Wang, Shao-Min,Zhu, Wei-Guo,Kang, Jian-Xun,Liu, Hong-Min,Chen, Jun-Miao,Li, Cui-Ping,Zhang, Kai
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- Direct Highly Regioselective Functionalization of Carbohydrates: A Three-Component Reaction Combining the Dissolving and Catalytic Efficiency of Ionic Liquids
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An unprecedented regioselective functionalization of unprotected polyols has been realized with the use of an ionic liquid NHC precatalyst. The protocol is robust, scalable, and the products can be isolated in good to excellent yields without chromatography. Moreover, the methodology enables successful recycling of the catalyst.
- Axelsson, Anton,Ta, Linda,Sundén, Henrik
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- Biosynthesis of methyl glucoside and its antibacterial activity against Staphylococcus aureus and Escherichia coli
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In this study, the methyl glucosides (MGn) was synthesized using β-cyclodextrin (β-CD) and methanol through the coupling reaction of recombinant cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans A11. The optimal condition for the synthesis of MGn consisted of an incubation of 1.5% (w/v) β-CD and 500 U/mL of CGTase in a water/methanol solution containing 30% (v/v) methanol at pH 6.0, 50 °C for 120 h. Upon analysis by TLC, at least three MG products were observed. The molecular weight of the main transferred product was 217.08 Da; this value was in accordance with methyl monoglucoside (MG1). MG1 was produced and prepared on a large scale and subsequently purified by preparative TLC. The combined 1H- and 13C-NMR analysis confirmed that the structure of MG1 was methyl-α-D-glucopyranoside. In addition, MG1 showed emulsification activity and stability in its formation in water and n-hexadecane. The antibacterial activity of MG1 was also determined by agar disc diffusion method. The results found that the MG1 (1, 5 and 10 mg/disc) showed antibacterial activity against E. coli ATCC 25922 only, with inhibition zones of 28, 38 and 40 mm, respectively. The MIC values (mg/mL) of MG1 against S. aureus ATCC 25923 and E. coli ATCC 25922 were found to be 20.00 and 0.63, while MBC values (mg/mL) were 40.00 and 0.63, respectively.
- Kaulpiboon, Jarunee,Rudeekulthamrong, Prakarn
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- Debenzylation of complex oligosaccharides using ferric chloride
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Anhydrous FeCl3 in CH2Cl2 at room temperature and 0°C has been used to debenzylate monosaccharides and oligosaccharides in yields generally greater than 70%. Notably, alkenes, acetates, benzoates, phthalimides, acyl amides, and sensitive glycosidic linkages are unaffected by the reaction conditions.
- Rodebaugh, Robert,Debenham, John S.,Fraser-Reid, Bert
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Read Online
- SELECTIVE VALORIZATION OF BIOMASS SUGARS
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Disclosed are methods of forming an epimer or a dehydrated isomer of a pyranose monosaccharide or a pyranose saccharide residue in an oligosaccharide or a glycoside.
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Page/Page column 47-51
(2021/06/26)
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- Triethylamine-methanol mediated selective removal of oxophenylacetyl ester in saccharides
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A highly selective, mild, and efficient method for the cleavage of oxophenylacetyl ester protected saccharides was developed using triethylamine in methanol at room temperature. The reagent proved successful against different labile groups like acetal, ketal, and PMB and also generated good yields of the desired saccharides bearing lipid esters. Further, we also observed DBU in methanol as an alternative reagent for the deprotection of acetyl, benzoyl, and oxophenylacetyl ester groups. This journal is
- Rasool, Javeed Ur,Kumar, Atul,Ali, Asif,Ahmed, Qazi Naveed
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p. 338 - 347
(2021/01/29)
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- Carbon glycoside glycosylated tetravalent platinum compound as well as synthesis method and application thereof
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The invention provides a carbon glycoside glycosylated tetravalent platinum compound, a synthesis method and application thereof. R1 and R2 are independently C1-C4 lower alkanes, R3 is glucose, galactose, mannose and ribose, different sugars are used as raw materials, and a series of carbon glycoside glycosylated tetravalent platinum compounds are synthesized through protection and deprotection reaction and metallization reaction of the sugars. The synthesis method is simple, the used raw materials are cheap and easy to obtain, the glycosylated tetravalent platinum compound has the capacity of targeting glucose transporter protein and has potential application value in the field of cancer treatment, introduction of a C-glucosidic bond enables the series of compounds to have the capacity of resisting hydrolysis of beta-glucosidase, and the compound is expected to be applied to the field of oral antitumor drugs.
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Paragraph 0064-0067
(2021/07/08)
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- Calixanthomycin A: Asymmetric Total Synthesis and Structural Determination
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We report the first asymmetric total synthesis and structural determination of calixanthomycin A. Taking advantage of a modular strategy, a concise approach was developed to assemble the hexacyclic skeleton with both enantiomers of the lactone A ring. Stereoselective glycosylation coupled the angular hexacyclic framework with a monosaccharide fragment to produce calixanthomycin A and its stereoisomers. This enable us to determine and assign the absolute configuration of C-25 (25S) and monosaccharide (derivative of l-glucose).
- Chen, Kuanwei,Xie, Tao,Shen, Yanfang,He, Haibing,Zhao, Xiaoli,Gao, Shuanhu
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supporting information
p. 1769 - 1774
(2021/03/08)
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- Both d - And l -Glucose Polyphosphates Mimic d - myo-Inositol 1,4,5-Trisphosphate: New Synthetic Agonists and Partial Agonists at the Ins(1,4,5)P3Receptor
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Chiral sugar derivatives are potential cyclitol surrogates of the Ca2+-mobilizing intracellular messenger d-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. Six novel polyphosphorylated analogues derived from both d- and l-glucose were synthesized. Binding to Ins(1,4,5)P3 receptors [Ins(1,4,5)P3R] and the ability to release Ca2+ from intracellular stores via type 1 Ins(1,4,5)P3Rs were investigated. β-d-Glucopyranosyl 1,3,4-tris-phosphate, with similar phosphate regiochemistry and stereochemistry to Ins(1,4,5)P3, and α-d-glucopyranosyl 1,3,4-tris-phosphate are full agonists, being equipotent and 23-fold less potent than Ins(1,4,5)P3, respectively, in Ca2+-release assays and similar to Ins(1,4,5)P3 and 15-fold weaker in binding assays. They can be viewed as truncated analogues of adenophostin A and refine understanding of structure-activity relationships for this Ins(1,4,5)P3R agonist. l-Glucose-derived ligands, methyl α-l-glucopyranoside 2,3,6-trisphosphate and methyl α-l-glucopyranoside 2,4,6-trisphosphate, are also active, while their corresponding d-enantiomers, methyl α-d-glucopyranoside 2,3,6-trisphosphate and methyl α-d-glucopyranoside 2,4,6-trisphosphate, are inactive. Interestingly, both l-glucose-derived ligands are partial agonists: they are among the least efficacious agonists of Ins(1,4,5)P3R yet identified, providing new leads for antagonist development.
- Shipton, Megan L.,Riley, Andrew M.,Rossi, Ana M.,Brearley, Charles A.,Taylor, Colin W.,Potter, Barry V. L.
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p. 5442 - 5457
(2020/07/21)
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- Acceleration and deceleration factors on the hydrolysis reaction of 4,6-O-benzylidene acetal group
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The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS? were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both Ea/ΔH? and A/ΔS? were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.
- Maki, Yuta,Kajihara, Yasuhiro,Nomura, Kota,Okamoto, Ryo,Izumi, Masayuki,Mizutani, Yasuhisa
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supporting information
p. 15849 - 15856
(2021/01/18)
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- Structure of the unusual Sinorhizobium fredii HH103 lipopolysaccharide and its role in symbiosis
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Rhizobia are soil bacteria that form important symbiotic associations with legumes, and rhizobial surface polysaccharides, such as K-antigen polysaccharide (KPS) and lipopolysaccharide (LPS), might be important for symbiosis. Previously, we obtained a mutant of Sinorhizobium fredii HH103, rkpA, that does not produce KPS, a homopolysaccharide of a pseudaminic acid derivative, but whose LPS electrophoretic profile was indistinguishable from that of the WT strain. We also previously demonstrated that the HH103 rkpLMNOPQ operon is responsible for 5-acetamido-3,5,7,9-tetradeoxy-7-(3-hydroxybutyramido)-L-glyc-ero-L-manno-nonulosonic acid [Pse5NAc7(3OHBu)] production and is involved in HH103 KPS and LPS biosynthesis and that an HH103 rkpM mutant cannot produce KPS and displays an altered LPS structure. Here, we analyzed the LPS structure of HH103 rkpA, focusing on the carbohydrate portion, and found that it contains a highly heterogeneous lipid A and a peculiar core oligosaccharide composed of an unusually high number of hexuronic acids containing b-configured Pse5NAc7(3OHBu). This pseudaminic acid derivative, in its a-configuration, was the only structural component of the S. fredii HH103 KPS and, to the best of our knowledge, has never been reported from any other rhizobial LPS. We also show that Pse5NAc7(3OHBu) is the complete or partial epitope for a mAb, NB6-228.22, that can recognize the HH103 LPS, but not those of most of the S. fredii strains tested here. We also show that the LPS from HH103 rkpM is identical to that of HH103 rkpA but devoid of any Pse5NAc7(3OHBu) residues. Notably, this rkpM mutant was severely impaired in symbiosis with its host, Macroptilium atropurpureum.
- Di Lorenzo, Flaviana,Speciale, Immacolata,Silipo, Alba,Alías-Villegas, Cynthia,Acosta-Jurado, Sebastián,Rodríguez-Carvajal, Miguel-ángel,Dardanelli, Marta S.,Palmigiano, Angelo,Garozzo, Domenico,Ruiz-Sainz, José-Enrique,Molinaro, Antonio,Vinardell, José-María
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p. 10969 - 10987
(2021/01/07)
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- Chemical constituents of the aerial parts of Algerian Galium brunneum: Isolation of new hydroperoxy sterol glucosyl derivatives
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The liposoluble extract of Galium brunneum aerial parts from North-eastern Algeria was chemically investigated. The EtOAc soluble portion contained a series of glycosyl cucurbitacins and sterols including three new glucosyl hydroperoxy sterols 1–3 among other phenolic components whereas the BuOH soluble fraction was dominated by glycosyl derivatives of flavonoids, iridoids and lignans, according to the chemistry reported in the literature for the genus Galium. The structure of new oxidized sterols 1–3 was determined by spectroscopic methods as well as by comparison with related known metabolites. Selected main compounds from both extracts, which revealed moderate antibacterial activities, were tested for their growth inhibitory properties against Gram-positive and Gram-negative bacteria. This is the first report of cucurbitacins in plants of genus Galium.
- Bertella, Anis,Bitam, Fatma,Carbone, Marianna,Ciavatta, Maria Letizia,Gavagnin, Margherita,Smadi, Abla
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- Methyl glycosides via Fischer glycosylation: translation from batch microwave to continuous flow processing
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Abstract: A continuous flow procedure for the synthesis of methyl glycosides (Fischer glycosylation) of various monosaccharides using a heterogenous catalyst has been developed. In-depth analysis of the isomeric composition was undertaken and high consistency with corresponding results observed under microwave heating was obtained. Even in cases where addition of water was needed to achieve homogeneity—a prerequisite for the flow experiments—no detrimental effect on the conversion was found. The scalability was demonstrated on a model case (mannose) and as part of the target-oriented synthesis of d-glycero-d-manno heptose, both performed on multigram scale.
- Aronow, Jonas,Stanetty, Christian,Baxendale, Ian R.,Mihovilovic, Marko D.
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- Kinetically Controlled Fischer Glycosidation under Flow Conditions: A New Method for Preparing Furanosides
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Kinetically controlled Fischer glycosidation was achieved under flow conditions. β-Hydroxy-substituted sulfonic acid functionalized silica (HO-SAS) was used as an acid catalyst. This reaction directly converted aldohexoses into kinetically favored furanosides to enable the practical synthesis of furanosides. After optimization of the reaction temperature and residence time, glucofuranosides, galactofuranosides, and mannofuranosides were synthesized in good yields.
- Masui, Seiji,Manabe, Yoshiyuki,Hirao, Kohtaro,Shimoyama, Atsushi,Fukuyama, Takahide,Ryu, Ilhyong,Fukase, Koichi
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supporting information
p. 397 - 400
(2019/02/26)
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- Introducing Oxo-Phenylacetyl (OPAc) as a Protecting Group for Carbohydrates
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A series of oxo-phenylacetyl (OPAc)-protected saccharides, with divergent base sensitivity profiles against benzoyl (Bz) and acetyl (Ac) were synthesized, and KHSO5/AcCl in methanol was identified as an easy, mild, selective, and efficient deprotecting reagent for their removal in the perspective of carbohydrate synthesis. Timely monitoring of AcCl reagent was supportive in both sequential and simultaneous deprotecting of OPAc, Bz, and Ac. The salient feature of our method is the orthogonal stability against different groups, its ease to generate different valuable acceptors using designed monosaccharides, and use of OPAc as a glycosyl donar.
- Kumar, Atul,Gannedi, Veeranjaneyulu,Rather, Suhail A.,Vishwakarma, Ram A.,Ahmed, Qazi Naveed
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p. 4131 - 4138
(2019/04/30)
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- Catalytic glycosylation of glucose with alkyl alcohols over sulfonated mesoporous carbons
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Herein we investigated the catalytic performances of sulfonated mesoporous carbons in the glycosylation of carbohydrates with alkyl alcohols. Catalytic performances were compared to common solid acid catalysts previously reported for this reaction. Under optimized conditions, the targeted alkyl glycosides were obtained in 85% yield, together with a turn over frequency and a space time yield higher than those of the best heterogeneous catalysts reported so far in such reaction. Furthermore, the presence of mesoporous channels significantly lowered the deactivation rate of the catalyst in comparison to a non-porous sulfonated carbon.
- Ramdani, Wahiba Ghezali,Karam, Ayman,De Oliveira Vigier, Karine,Rio, Sébastien,Ponchel, Anne,Jér?me, Fran?ois
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p. 125 - 129
(2019/03/06)
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- Production of lactic acid derivatives from sugars over post-synthesized Sn-Beta zeolite promoted by WO3
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Various metal oxides were used as co-catalysts to improve the production of alkyl lactate over Sn-Beta-P. WO3 exhibited the best promotion effect. The yield of MLA increased from 25% (6.5 g L?1) over Sn-Beta-P (0.2 g) to 52% (13.4 g L?1) over WO3 (0.1 g) and Sn-Beta-P (0.1 g) at 160 °C for 5 h and 3.1 wt% of glucose concentration. MLA yield of 38% was attained even at glucose concentration of 10 wt% and the space-time yield reached 7.1 g L?1 h?1. The action mechanism of WO3 was investigated. Fine WO3 particles adsorbed on surface of Sn-Beta-P in reaction media and decreased the silanol defects of Sn-Beta-P. This promotes retro-aldol of fructose, the rate-determining step of whole reaction, thus facilitated the formation of MLA. Kinetic studies indicate that the presence of WO3 decreased the activation energy of the retro-aldol of fructose. The binary solid WO3 and Sn-Beta-P is recyclable.
- Yang, Xiaomei,Zhang, Yali,Zhou, Lipeng,Gao, Beibei,Lu, Tianliang,Su, Yunlai,Xu, Jie
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p. 285 - 291
(2019/03/21)
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- From d-to l-Monosaccharide Derivatives via Photodecarboxylation-Alkylation
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Photodecarboxylation-alkylation of conformationally locked monosaccharides leads to inversion of stereochemistry at C5. This allows the synthesis of l-sugars from their readily available d-counterparts. Via this strategy, methyl l-guloside was synthesized from methyl d-mannoside in 21% yield over six steps.
- Wan, I. C. Steven,Witte, Martin D.,Minnaard, Adriaan J.
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supporting information
p. 7669 - 7673
(2019/10/08)
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- A novel enzymatic method for the synthesis of methyl 6-O-acetyl-α-D-glucopyranoside using a fermented solid containing lipases produced by Burkholderia contaminans LTEB11
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Chemical methods for the regioselective modification of carbohydrates require several steps that involve the addition and removal of protective groups. Enzymatic methods are promising since they can give high selectivity in a single step. We developed a new method for acetylation of methyl-α-D-glucopyranoside with vinyl acetate, the reaction being catalyzed by a fermented solid containing lipases from Burkholderia contaminans LTEB11. The main product of the synthesis, methyl 6-O-acetyl-α-D-glucopyranoside (6-OAc-α-MetGlc), was identified by NMR and quantified by HPLC. The conversion of methyl-α-D-glucopyranoside to 6-OAc-α-MetGlc was evaluated at laboratory scale (4 mL) in different solvent systems. The conversion increased with increasing hydrophobicity of the solvent, with the highest conversion, 65% in 72 h, being obtained in the solvent-free system. This system was scaled up to a 1-L reaction medium. A conversion of 76% in 72 h was obtained, with a calculated yield of 1.05 g (4.43 mmol) of 6-OAc-α-MetGlc. This is the largest amount of 6-OAc-α-MetGlc (in moles) produced by enzymatic catalysis that has been reported in the literature to date. These results suggest that the fermented solid produced by B. contaminans LTEB11, which is a low-cost biocatalyst, could potentially be used for the industrial production of esters of α-D-glucose.
- Villalobos, Maribel Cordero,Gon?alves, Alan Guilherme,Noseda, Miguel Daniel,Mitchell, David Alexander,Krieger, Nadia
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- Structure elucidation of a novel oligosaccharide (Medalose) from camel milk
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Free oligosaccharides are the third most abundant solid component in milk after lactose and lipids. The study of milk oligosaccharides indicate that nutrients are not only benefits the infant's gut but also perform a number of other functions which include stimulation of growth, receptor analogues to inhibit binding of pathogens and substances that promote postnatal brain development. Surveys reveal that camel milk oligosaccharides possess varied biological activities that help in the treatment of diabetes, asthma, anaemia, piles and also a food supplement to milking mothers. In this research, camel milk was selected for its oligosaccharide contents, which was then processed by Kobata and Ginsburg method followed by the HPLC and CC techniques. Structure elucidation of isolated compound was done by the chemical degradation, chemical transformation and comparison of chemical shift of NMR data of natural and acetylated oligosaccharide structure reporter group theory, the 1H, 13C NMR, 2D-NMR (COSY, TOCSY and HSQC) techniques, and mass spectrometry. The structure was elucidated as under: MEDALOSE[Figure presented]
- Gangwar, Lata,Singh, Rinku,Deepak, Desh
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p. 157 - 161
(2017/10/13)
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- Synthesis of alkyl α- and β-d-glucopyranoside-based chiral crown ethers and their application as enantioselective phase-transfer catalysts
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Chiral monoaza-15-crown-5-type lariat ethers annelated to alkyl 4,6-O-benzylidene-α- and β-d-glucopyranosides have been synthesized. These macrocycles generated significant asymmetric induction as phase-transfer catalysts in a few two-phase reactions. The catalytic effect of the lariat ethers with methoxy, ethoxy, and i-propoxy substituents on C-1 of the sugar unit in both α and β positions was compared. In liquid–liquid two-phase reactions, the nature and position of the substituents did not have much effect. The α-anomers were somewhat more efficient in terms of enantioselectivity than the β forms. In asymmetric Darzens condensations, in the epoxidation of trans-chalcone, in the Michael addition of β-nitrostyrene and diethyl acetamidomalonate, and in the reaction of 2-benzylidene-1,3-indandione with diethyl bromomalonate, maximum enantioselectivities of 73, 94, 78, and 72%, respectively, were obtained in presence of glucopyranoside-based lariat ethers as catalysts.
- Pálv?lgyi, ádám,Rapi, Zsolt,Ozohanics, Olivér,Tóth, Gábor,Keglevich, Gy?rgy,Bakó, Péter
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p. 1627 - 1645
(2017/11/16)
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- Antimycobacterial 1,4-napthoquinone natural products from Moneses uniflora
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A new 1,4-naphthoquinone derivative, 5,8-dihydro-3-hydroxychimaphilin (4) and five known compounds (1, 2 and 5–7) were isolated from an extract of the Canadian medicinal plant Moneses uniflora that significantly inhibited the growth of Mycobacterium tuberculosis H37Ra. The structure of 4 was established through analysis of NMR and MS data and the absolute configuration of the glycone of 5 was determined by chemical transformation and comparison with standards prepared from D- and L-glucose. All compounds isolated were screened against Mycobacterium tuberculosis (H37Ra) and the mammalian HEK 293 cell line and, with the exception of compounds 5 and 7, exhibited marked selectivity in their bioactivity: Compound 1 exhibited potent antimycobacterial activity (IC50 of 5.4 μM) and moderate cytotoxicity (IC50 of 30 μM); compounds 2, 4 and 6 showed moderate antimycobacterial activity (IC50 values from 28 to 47 μM) without affecting the viability of mammalian cells; compound 5 displayed moderate activity in both assays (IC50 values of 44 and 55 μM respectively); and compound 7 was not active in either assay. These data suggest that the Moneses napthaquinone derivatives elicit biological responses in mycobacterial and mammalian cells through disparate modes of action that warrant further investigation.
- Li, Haoxin,Bos, Allyson,Jean, Stéphanie,Webster, Duncan,Robichaud, Gilles A.,Johnson, John A.,Gray, Christopher A.
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p. 229 - 233
(2018/08/21)
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- Synthesis of Rare Deoxy Amino Sugar Building Blocks Enabled the Total Synthesis of a Polysaccharide Repeating Unit Analogue from the LPS of Psychrobacter cryohalolentis K5T
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Lipopolysaccharides (LPSs) play key roles in humoral immunity. Recently, the LPS structure of the Psychrobacter cryohalolentis K5T strain was reported. Due to the presence of unnatural amino sugars and branched linkages, its structure is unique. Herein we report the total synthesis of an LPS analogue of P. cryohalolentis K5T. After overcoming the issues like ring conformation changes and elimination of triflate, we were able to develop a strategy for the synthesis of the newly reported 2,3,4-triacetamido-2,3,4-trideoxy-l-arabinose derivative. Coupling of different donors with suitable acceptors from the nonreducing end to the reducing end and further functional group modifications delivered the protected LPS hexasaccharide repeating unit. After functional group modifications, we were unable to oxidize the hindered primary hydroxyl group to synthesize the target molecule. Alternatively, removal of the permanent protecting groups afforded the LPS hexasaccharide repeating unit analogue of Psychrobacter cryohalolentis K5T.
- Emmadi, Madhu,Kulkarni, Suvarn S.
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p. 14323 - 14337
(2018/11/25)
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- Kinetic analysis of hexose conversion to methyl lactate by Sn-Beta: Effects of substrate masking and of water
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Simple sugars show promise as substrates for the formation of fuels and chemicals using heterogeneous catalysts in alcoholic solvents. Sn-Beta is a particularly well-suited catalyst for the cleavage, isomerization and dehydration of sugars into more valuable chemicals. In order to understand these processes and save resources and time by optimising them, kinetic and mechanistic analyses are helpful. Herein, we study substrate entry into the Sn-Beta-catalysed methyl lactate process using abundant hexose substrates. NMR spectroscopy is applied to show that the formation of methyl lactate occurs in two kinetic regimes for fructose, glucose and sucrose. The majority of methyl lactate is not formed from the substrate directly, but from methyl fructosides in a slow regime. At 160 °C, more than 40% of substrate carbon are masked (i.e. reversibly protected in situ) as methyl fructosides within a few minutes when using hydrothermally synthesised Sn-Beta, while more than 60% methyl fructosides can be produced within a few minutes using post-synthetically treated Sn-Beta. A significant fraction of the substrate is thus masked by rapid methyl fructoside formation prior to subsequent slow release of fructose. This release is the rate-limiting step in the Sn-Beta-catalysed methyl lactate process, but it can be accelerated by the addition of small amounts of water at the expense of the maximum methyl lactate yield.
- Tosi, Irene,Riisager, Anders,Taarning, Esben,Jensen, Pernille Rose,Meier, Sebastian
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p. 2137 - 2145
(2018/05/04)
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- From organocatalysed desilylations to high-yielding benzylidenations of electron-deficient benzaldehydes
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A new type of organoprecatalyst (MeSCH2Cl/KI) for desilylation and benzylidenation reactions has been designed. Both reactions are user friendly and high yielding (71->99%) and have fast reaction rates. The desilylation of iodo silyl ethers was achieved with no sequential etherification side reactions like those seen for reactions when using TBAF. In the application of the catalytic system to a 6-TBDMS ether of a glucoside, glucoside benzylidenations using electron-deficient benzaldehydes were achieved in 87% yield compared with the previously reported yields of 69-77%. Altogether, 14 benzylidenation reactions were realised using silyloxy alcohols and electrondeficient benzaldehydes instead of their activated acetal forms. In terms of reaction rates and yields, the order of the benzylidenations is p-fluorobenzaldehyde > benzaldehyde > p-anisaldehyde, and a possible mechanism is discussed. These experiments have preliminarily differentiated this cost-effective catalytic system from the classic Lewis acids.
- Niu, Qun,Xing, Linlin,Li, Chunbao
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p. 358 - 364
(2017/06/19)
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- Structurally Simple Benzylidene-Type Photolabile Diol Protecting Groups
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Two structurally simple photolabile protecting groups for releasing 1,2- and 1,3-diols have been developed. The diols can be protected in high yields and released from their corresponding acetals with high chemical efficiency.
- Ding, Xiong,Devalankar, Dattatray A.,Wang, Pengfei
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supporting information
p. 5396 - 5399
(2016/11/06)
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- A practical and efficient synthesis of methyl levulinate from cellulosic biomass catalyzed by an aluminum-based mixed acid catalyst system
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Methyl levulinate is a promising building block which can be derived from cellulosic biomass. In this paper, a combination of aluminum compounds and organic sulfonic acids was found to be an efficient catalyst system for direct methyl levulinate synthesis from both microcrystalline cellulose and wood powder. Electrospray ionization mass analysis revealed the formation of aluminum sulfonate complexes in the reaction solution. The reaction properties of this catalyst system suggested that cooperative catalysis of aluminum sulfonates and organic sulfonic acids in methanol was responsible for the efficient formation of methyl levulinate.
- Tominaga,Nemoto,Kamimura,Yamada,Yamamoto,Sato
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p. 65119 - 65124
(2016/07/23)
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- Mesoporous H-ZSM-5 as an efficient catalyst for conversions of cellulose and cellobiose into methyl glucosides in methanol
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The alcoholysis of cellobiose, which is a dimer of glucose and a model molecule of cellulose, has been studied in methanol medium in the presence of various solid acids. Zeolite H-ZSM-5 was found to be highly efficient for the conversion of cellobiose into methyl glucosides (including methyl-α-glucoside and methyl-β-glucoside) in methanol. The Br?nsted acidity plays a key role in the catalytic alcoholysis of cellobiose. H-ZSM-5 with a lower Si/Al ratio (20) possessed higher density of acidic sites afforded a higher methyl glucoside yield (53%) for the conversion of cellobiose at 423 K. The introduction of mesoporosity into the zeolite significantly enhanced its catalytic performance. Methyl glucosides with a yield of 73% were achieved from cellobiose over a mesoporous H-ZSM-5 (H-meso-ZSM-5-0.5 M) sample with an average mesopore size of 6.1 nm. The mesoporous ZSM-5 could also catalyze the direct transformation of cellulose in methanol, providing methyl glucosides with yields of 51% at 463 K. Our comparative studies revealed that the alcoholysis of cellulose in methanol proceeded more efficiently than the hydrolysis of cellulose in water under similar reaction conditions.
- Xue, Laiqi,Cheng, Kang,Zhang, Hongxi,Deng, Weiping,Zhang, Qinghong,Wang, Ye
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- Flavonoid glycosides from Siparuna gigantotepala leaves and their antioxidant activity
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Two new flavonol g1lycosides were isolated from the leaves of Siparuna gigantotepala. Their structures were determined to be kaempferol 3-O-β-xylopyranosyl-(1→2)-α-arabinofuranoside (1) and kaempferol 3,7-di-O-methyl-4′-O-α-rhamnopyranosyl-(1→2)-β-glucopy
- Casta?eda, Harlen Gerardo Torres,Dulcey, Ana Julia Colmenares,Martínez, José Hipólito Isaza
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p. 502 - 506
(2016/06/01)
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- Isolation, structure elucidation and DFT study on two novel oligosaccharides from yak milk
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Two novel oligosaccharides were isolated from yak milk. The milk was processed by the method of Kobata and Ginsberg involving deproteination, centrifugation and lyophilization followed by gel filtrate chromatography acetylation and silica gel column chromatography of derivatized oligosaccharides while their homogeneity was confirmed by HPLC. The structures of these isolated oligosaccharides were elucidated by chemical transformation, chemical degradation, 1H, 13C NMR, 2D NMR (COSY, TOCSY and HSQC) and mass spectrometry. The geometry of compound A (Bosiose) and B (Bovisose) have been optimized at B3LYP method and 6-311 + G(d,p) basis set. The difference between the energies of A and B is 1.269 a.u. or 796.309 kcal/mol.
- Singh, Meenakshi,Kumar, Alok,Srivastava, Gaurav,Deepak, Desh,Singh
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- The synthesis and antitumor activity of twelve galloyl glucosides
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Twelve galloyl glucosides 1-12, showing diverse substitution patterns with two or three galloyl groups, were synthesized using commercially available, low-cost D-glucose and gallic acid as starting materials. Among them, three compounds, methyl 3,6-di-O-galloyl-?±-D-glucopyranoside (9), ethyl 2,3-di-O-galloyl-?±-D-glucopyranoside (11) and ethyl 2,3-di-O-galloyl-?2-D-glucopyranoside (12), are new compounds and other six, 1,6-di-O-galloyl-?2-D-glucopyranose (1), 1,4,6-tri-O-galloyl-?2-D-glucopyranose (2), 1,2-di-O-galloyl-?2-D-glucopyranose (3), 1,3-di-O-galloyl-?2-D-glucopyranose (4), 1,2,3-tri- O-galloyl-?±-D-glucopyranose (6) and methyl 3,4,6-tri-O-galloyl-?±-D-glucopyranoside (10), were synthesized for the first time in the present study. In in vitro MTT assay, 1-12 inhibited human cancer K562, HL-60 and HeLa cells with inhibition rates ranging from 64.2% to 92.9% at 100 ??g/mL, and their IC50 values were determined to be varied in 17.2-124.7 ??M on the tested three human cancer cell lines. In addition, compounds 1-12 inhibited murine sarcoma S180 cells with inhibition rates ranging from 38.7% to 52.8% at 100 ??g/mL in the in vitro MTT assay, and in vivo antitumor activity of 1 and 2 was also detected in murine sarcoma S180 tumor-bearing Kunming mice using taxol as positive control.
- Li, Chang-Wei,Dong, Hua-Jin,Cui, Cheng-Bin
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p. 2034 - 2060
(2015/03/05)
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- Enhanced basicity of Ag2O by coordination to soft anions
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In Ag2O-mediated benzylation, the addition of a catalytic amount of KI can greatly improve reactivity. This is usually attributed to the formation of a more reactive iodo-substituted electrophile. However, our studies show this to be due to the enhanced basicity of Ag2O through coordination of soft iodide anions to the silver atom, and show KI to be an initiator. A catalytic amount of Ag2O and NaBr can catalyze transesterification reactions, indicating the enhanced basicity of Ag2O by bromide. We believe that this is a general effect for metal oxides and soft anions, applicable to a wider range of organic reaction systems. All your base belongs to us: In Ag2O-mediated benzylation, the addition of a catalytic amount of KI can greatly improve reactivity. Our studies show this to be attributable to the enhanced basicity of Ag2O through coordination of soft iodide anions to the silver atom, and show KI to be an initiator. Thus, NaBr as an initiator combined with Ag2O has been successfully used to catalyze transesterification reactions.
- Ren, Bo,Wang, Meiyan,Liu, Jingyao,Ge, Jiantao,Dong, Hai
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p. 761 - 765
(2015/03/04)
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- Metal-catalyzed stereoselective and protecting-group-free synthesis of 1,2-cis-glycosides using 4,6-dimethoxy-1,3,5-triazin-2-yl glycosides as glycosyl donors
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4,6-Dimethoxy-1,3,5-triazin-2-yl glycosides, glycosyl donors prepared in one step from free saccharides without protection of the hydroxy groups, were stereoselectively and equivalently converted to the corresponding 1,2-cis-glycosides by using a catalytic amount of metal catalyst. This reaction was successfully applied not only to monosaccharides, but also to di- and oligosaccharides.
- Tanaka, Tomonari,Kikuta, Naoya,Kimura, Yoshiharu,Shoda, Shin-Ichiro
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supporting information
p. 846 - 848
(2015/06/22)
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- Zemplén transesterification: A name reaction that has misled us for 90 years
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We demonstrated that using NaOH and NaOMe in methanol for deacylation are identical, indicating that the Zemplén condition has been misleading us for almost 90 years. The traditional base-catalyzed mechanism cannot be used to explain our results. We propose that H-bond complexes play key roles in the base-catalyzed process, explaining why deacylation in methanol can be catalyzed by hydroxide.
- Ren, Bo,Wang, Meiyan,Liu, Jingyao,Ge, Jiantao,Zhang, Xiaoling,Dong, Hai
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supporting information
p. 1390 - 1394
(2015/03/18)
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- Quinofuracins A-E, produced by the fungus staphylotrichum boninense PF1444, show p53-dependent growth suppression
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Quinofuracins A-E, novel anthraquinone derivatives containing β-d-galactofuranose that were isolated from the fungus Staphylotrichum boninense PF1444, induced p53-dependent cell death in human tumor cells. The structures of quinofuracins A-E, including absolute configurations, were elucidated by extensive spectroscopic analysis and chemical transformation studies. Quinofuracins were classified into three groups according to the aglycone moieties. 5'-Oxoaverantin was present in quinofuracins A-C, whereas averantin and versicolorin B were identified in quinofuracins D and E, respectively. These quinofuracins induced p53-dependent growth suppression in human glioblastoma LNZTA3 cells.
- Tatsuda, Daisuke,Momose, Isao,Someno, Tetsuya,Sawa, Ryuichi,Kubota, Yumiko,Iijima, Masatomi,Kunisada, Takao,Watanabe, Takumi,Shibasaki, Masakatsu,Nomoto, Akio
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supporting information
p. 188 - 195
(2015/03/18)
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- Effect of metal salts existence during the acid-catalyzed conversion of glucose in methanol medium
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Catalytic effect of various metal salts as co-catalyst of sulfuric acid was examined.The reaction selectivity is a clear function of the type of metal salts.The major product was methyl glucoside in the presence of K2SO4 or Na2SO4.For Fe2(SO4)3 and Al2(SO4)3, methyl levulinate was formed in the highest yields.Alkali metal sulfates can suppress methyl glucoside isomerize to methyl fructoside.
- Peng, Lincai,Li, Hui,Lin, Lu,Chen, Keli
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- Catalytic reductive cleavage of methyl α-d-glucoside acetals to ethers using hydrogen as a clean reductant
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The palladium-catalysed reductive cleavage of methyl glucoside acetals has been studied using hydrogen as a clean reducing agent. The reaction proceeds at 120 °C in cyclopentyl methyl ether (CPME) without acid co-catalyst. Under these conditions, the corresponding methyl glucoside monoethers were obtained with poor to good isolated yields (37-81%) and high selectivities (86-99%). This journal is
- Gozlan, Charlotte,Lafon, Romain,Duguet, Nicolas,Redl, Andreas,Lemaire, Marc
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p. 50653 - 50661
(2015/02/19)
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- Protecting-group-free O-glysosidation using p-toluenesulfonohydrazide and glycosyl chloride donors
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A range of N′-glycosylsulfonohydrazides (GSHs) display good reactivity but poor stereoselectivity in protecting-group-free O-glycosidations when a moderate excess of the model acceptor n-decanol is employed. This stable, readily-accessed class of donor may be more tractable for the glycosylation of non-volatile acceptors than Fischer's glycosidation conditions. It is possible to generate unprotected glycosyl chlorides from GSHs in situ. In an effort to find conditions to improve glycosidation stereoselectivity, methanolysis of unprotected glucosyl chloride under halide-ion exchange conditions was examined. Relative to its tetra-O-benzyl analogue, this donor displays moderate, inverted stereoselectivity and a significantly faster reaction rate.
- Williams, Rohan J.,Paul, Caroline E.,Nitz, Mark
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- Lipid metabolites with free-radical scavenging activity from Euphorbia helioscopia L.
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The methanolic extract of the plant Euphorbia helioscopia L. exhibited an interesting free-radical scavenging activity. From the aerial parts of Euphorbia helioscopia L. (Euphorbiaceae), a complex mixture of seven cerebrosides together with glucoclionasterol, a digalactosyldiacylglycerol and a diacylmonogalactosylglycerol were identified. The structures of the cerebrosides were characterized as 1-O-β-d-glucosides of phytosphingosines, which comprised (2S, 3S, 4E, 8E)-2-amino-4(E),8(E)-octadecadiene-1,3-diol, (2S, 3S, 4E, 8Z)-2-amino-4(E),8(Z)-octadecadiene-1,3-diol, (2S, 3S, 4R, 8Z)-2-amino-8(Z)-octadecene-1,3,4-triol as long chain bases with seven 2-hydroxy fatty acids of varying chain lengths (C16, C24:1, C 26:1, C24, C26, C28:1) linked to the amino group. The glycosylglycerides were characterized as (2S)-2,3-O-di-(9,12, 15-octadecatrienoyl)-glyceryl-6-O-(α-d-galactopyranosyl) -β-d-galactopyranoside and (2S)-2,3-O-di-(9,12,15-octadecatrienoyl)- glyceryl-1-O-β-d-galactopyranoside. The structures were established on the basis of spectroscopic data and chemical reactions.
- Cateni,Zilic,Altieri,Zacchigna,Procida,Gaggeri,Rossi,Collina
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- Protection-free synthesis of alkyl glycosides under hydrogenolytic conditions
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A convenient protection-free synthetic route for the preparation of alkyl glycosides has been developed. The alcoholysis of one-step preparable glycosyl donors, 4,6-dibenzyloxy-1,3,5-triazin-2-yl (DBT) glycosides, under hydrogenolytic conditions gave the corresponding glycosides in good yields without the addition of any acid promoters. The method could be successfully applied to the glycosylation of an acidlabile oligosaccharide.
- Ishihara, Masaki,Takagi, Yuka,Li, Gefei,Noguchi, Masato,Shoda, Shin-Ichiro
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p. 1235 - 1237
(2013/10/22)
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- METHOD FOR PRODUCING GLUCOSIDES
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The present invention relates to methods for producing glucosides directly from glucose or a polysaccharide comprising glucose as a structural unit. The present invention provides a method comprising reacting glucose or a polysaccharide comprising glucose as a structural unit with a compound represented by R—OH in the presence of a supercritical or subcritical carbon dioxide to produce glucosides and a method comprising dissolving or suspending glucose or a polysaccharide comprising glucose as a structural unit in an organic solvent containing a compound represent by R—OH and reacting the glucose or polysaccharide with the compound represented by R—OH in the presence of a supercritical or subcritical carbon dioxide to produce glucosides.
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Paragraph 0071-0103
(2013/03/26)
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- Two new sphingolipids from the leaves of Piper betle L.
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Two new sphingolipids, pipercerebrosides A (1) and B (2), were isolated from the leaves of Piper betle L. Their structures, including absolute configurations, were determined by spectroscopic analysis and chemical degradation. These two compounds did not show significant cytotoxic activity against the cancer cell lines K562 and HL-60 in a MTT assay.
- Chen, Duo-Zhi,Xiong, Hua-Bin,Tian, Kai,Guo, Jun-Ming,Huang, Xiang-Zhong,Jiang, Zhi-Yong
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p. 11241 - 11249
(2013/10/22)
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- Novel cerebrosides isolated from the fermentation mycelia of tuber indicum
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The four new cerebrosides 1-4 possessing a unique C18 9-methylsphinga-4,8-dienine-related moiety and a cyclic octapeptide, 5, possessing alternating proline and glycine moietes were isolated from the Tuber indicum fermentation mycelium. Their structures were established on the basis of a spectroscopic analysis including NMR and HR-ESI-MS, as well as an acidic methanolysis experiment. To the best of our knowledge, the cerebrosides identified in the present study are quite different from those isolated from Tuber indicum fruiting bodies. Additionally, it was the first time that a cyclic peptide was isolated from the Tuber genus. Copyright
- Li, Yuan-Yuan,Liu, Ping,Tang, Yang,Li, Hong-Mei,Tang, Ya-Ling,Liang, Xin-Hua,Tang, Ya-Jie
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p. 702 - 709
(2013/06/04)
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- Development of hydrophilic photolabile hydroxyl protecting groups
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Hydrophilic photolabile protecting groups (PPGs) for hydroxyl protection have been developed. The new PPGs are derived from 3-(dimethylamino)trityl (DMATr) by replacing the two methyl groups with two hydrophilic butyryl groups. The new PPG reagents can be readily prepared and installed. They are stable in the dark but can be removed cleanly and efficiently in aqueous environments upon irradiation with a UV lamp or sunlight.
- Yang, Haishen,Zhou, Lei,Wang, Pengfei
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scheme or table
p. 514 - 517
(2012/06/30)
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- Tuning methyl 4,6-O-benzylidene α-D-glucopyranosides' gelation ability by minor group modifications
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Ten methyl 4,6-O-benzylidene α-d-glucopyranosides were synthesized for the purpose of studying systematically the effect of small group changes at position 4 of the aromatic ring on the ability to gelate organic solvents. The gelation properties are discussed on the basis of small angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) measurements, and scanning electron microscopy (SEM) observations. Sol-gel transition temperatures were determined simultaneously by DSC and temperature-dependent FTIR measurements. The current study emphasizes that carbohydrates furnish not only valuable information about structural requirements for organogelator design, but also for molecular assembly systems in general.
- Abreu, Marlon F.,Salvador, Vítor T.,Vitorazi, Letícia,Gatts, Carlos E.N.,Dos Santos, Denise R.,Giacomini, Rosana,Cardoso, Sergio L.,Miranda, Paulo C.M.L.
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scheme or table
p. 69 - 78
(2012/07/02)
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- Mode of alkylation of alcohols with O-cyclopropylmethyl trichloroacetimidate and O-cyclobutyl trichloroacetimidate
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Acid promoted alkylation of hydroxy group containing acceptors 3-14 with O-cyclopropylmethyl and O-cyclobutyl trichloroacetimidates 1 and 2, respectively, afforded ethers with cyclopropylmethyl, cyclobutyl, and homoallyl residues as a result of the rearrangement of the cation intermediates. The dependence of product formation on acceptor structure is discussed. ARKAT-USA, Inc.
- Ali, Ibrahim A.I.,Zhu, Xiangming,El Ashry, El Sayed H.,Schmidta, Richard R.
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- Intramolecular glycosidation by click reaction mediated spacer generation followed by spacer cleavage
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2-O-Propargyl-substituted glycosyl donors and O-(2-azidobenzyl)-substituted acceptors having a vicinal hydroxy group readily underwent the click reaction. Intramolecular glycosidation with N-iodosuccinimide/trifluoromethansulfonic acid as the activating system afforded β-(1-3)- and α-(1-2)-linked disaccharides as part of 14-membered macrocycles. Descriptors for these reactions are proposed that consider the donor and acceptor attachment sites and the stereochemistry of the functional groups. Investigation of the influence of 2-O-linked 1-aryl-1,2,3-triazol-4-ylmethyl groups, as contained in the spacer, on the anomeric selectivity exhibited no anchimeric assistance. In addition, it was shown that the spacer group can be readily cleaved under Birch reduction conditions. The 1,2,3-triazole-forming click reaction was employed to generate glycosyl donor-spacer-acceptor constructs. Upon glycosidation, 14-membered macrocycles were obtained with high anomeric selectivity. Spacer cleavage was performed under Birch reduction conditions. Copyright
- Kumar, Amit,Geng, Yiqun,Schmidt, Richard R.
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p. 6846 - 6851
(2013/03/13)
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- Isolation and characterization of a novel α-glucosidase with transglycosylation activity from Arthrobacter sp. DL001
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A strain of Arthrobacter sp. DL001 with high transglycosylation activity was successfully isolated from the Yellow Sea of China. To purify the extracellular enzyme responsible for transglycosylation, a four-step protocol was adopted and the enzyme with electrophoretical purity was obtained. The purified enzyme has a molecular mass of 210 kDa and displays a narrow hydrolysis specificity towards α-1,4-glucosidic bond. Its hydrolytic activity was identified as decreasing in the order of maltotriose > panose > maltose. Only 3.61% maltose activity occurs when p-nitrophenyl α-d-glycopyranoside serves as a substrate, suggesting that this enzyme belongs to the type II α-glucosidase. In addition, the enzyme was able to transfer glucosyl groups from the donors containing α-1,4-glucosidic bond specific to glucosides, xylosides and alkyl alcohols in α-1,4- or α-1,6-manners. A decreased order of activity was observed when maltose, maltotriose, panose, β-cyclodextrin and soluble starch served as glycosyl donors, respectively. When maltose was utilized as a donor and a series of p-nitrophenyl-glycosides as acceptors, the glucosidase was capable of transferring glucosyl groups to p-nitrophenyl-glucosides and p-nitrophenyl-xylosides in α-1,4- or α-1,6-manners. The yields of p-nitrophenyl-oligosaccharides could reach 42-60% in 2 h. When a series of alkyl alcohols were utilized as acceptors, the enzyme exhibited its transglycosylation activities not only to the primary alcohols but also to the secondary alcohols with carbon chain length 1-4. Therefore, all the results indicated that the purified α-glucosidase present a useful tool for the biosynthesis of oligosaccharides and alkyl glucosides.
- Zhou, Kun,Luan, Hong-Wei,Hu, Ying,Ge, Guang-Bo,Liu, Xing-Bao,Ma, Xiao-Chi,Hou, Jie,Wang, Xiu-Li,Yang, Ling
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experimental part
p. 48 - 57
(2012/09/07)
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- New sphingolipids from Abutilon pakistanicum
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Pakistamides A and B (1 and 2, respectively), two new sphingolipids, have been isolated from the AcOEt-soluble sub-fraction of the MeOH extract of the whole plant of Abutilon pakistanicum. Their structures were assigned by 1 H and 13C NMR spectra, and by DEPT and COSY, NOESY, HMQC, HMBC, EI-MS, and FAB-MS experiments.
- Ali, Bakhat,Mehmood, Rashad,Hussain, Riaz,Malik, Abdul,Imran, Muhammad,Nawaz, Haq,Hussain, Ajaz
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experimental part
p. 433 - 437
(2012/08/14)
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- Spiraeamide, new sphingolipid from Spiraea brahuica
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Spiraeamide (1), a new sphingolipid, has been isolated from the ethyl acetate-soluble fraction of the methanolic extract of the whole plant of Spiraea brahuica, along with marrubiin (2), 19-acetylmarrubenol (3), and 6-acetylmarruenol (4). Their structures were elucidated by 1H and 13C NMR spectra, and COSY, NOESY, HMQC, HMBC, EI-MS, and FAB-MS experiments.
- Mughal, Uzma Rasheed,Mehmood, Rashad,Malik, Abdul,Ali, Bakhat,Safder, Muhammad,Tareen, Rasool Bakhsh
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experimental part
p. 601 - 606
(2012/08/28)
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- One-pot preparation of methyl levulinate from catalytic alcoholysis of cellulose in near-critical methanol
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One-pot preparation of methyl levulinate (MLA) from cellulose in near-critical methanol was studied. Acids containing SO3H group were proven to be effective catalysts for the production of MLA from cellulose's catalytic alcoholysis. The effects of different reaction conditions, such as an initial cellulose concentration of 10-30 g/L, a temperature range from 170 to 190 °C, and a sulfuric acid concentration of 0.01-0.03 mol/L, on the production of MLA were investigated. The results showed the reaction temperature and acid concentration significantly affected the process of cellulose alcoholysis and the yield of MLA. A high yield of up to 55% MLA was achieved at 190 °C for 5 h, using 0.02 mol/L H2SO4 as a catalyst.
- Wu, Xiaoyu,Fu, Jie,Lu, Xiuyang
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p. 37 - 39,3
(2020/07/31)
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- Characterization of ulvan extracts to assess the effect of different steps in the extraction procedure
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An effective application development of the polysaccharide ulvan requires a comprehensive knowledge about the influence of the extraction process on composition of the extracts and in ulvan itself. In this context, the two main objectives of the present work are (1) the establishment of an efficient extraction process for ulvan and (2) development of an accurate characterization methodology to evaluate the extract composition and ulvan content. Three ulvan-rich extracts obtained by different schemes of extraction were studied. The methodology for the analysis was improved and a detailed analysis of extracted ulvan was provided. The polysaccharide is rich in ulvanobiuronic acid 3-sulfate type A [→4)-β-d-GlcAp-(1 → 4)-α-l-Rhap 3S-(1→], with minor amounts of ulvanobiuronic acid 3-sulfate type B [→4)-α-l-IdoAp-(1 → 4)-α-l-Rhap 3S-(1→]. The extract with the higher degree of purification is a high molecular weight polysaccharide (790 kDa) composed of rhamnose (22.4%), glucuronic acid (22.5%), xylose (3.7%), iduronic acid (3.1%) and glucose (1.0%). It is highly sulfated (32.2%) and contains 1.3% of proteins and 10.3% of inorganic material. Applying simple extraction scheme it was possible to obtain an extract from green algae with high content of ulvan without affecting the overall chemical structure of the polysaccharide.
- Costa, Carina,Alves, Anabela,Pinto, Paula R.,Sousa, Rui A.,Borges Da Silva, Eduardo A.,Reis, Rui L.,Rodrigues, Alírio E.
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experimental part
p. 537 - 546
(2012/06/15)
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