- Synthesis and cytotoxicities of icogenin analogues with disaccharide residues
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For further structure-activity relationships (SAR) research of furostan saponin, two icogenin analogues: (25R)-22-O-methyl-furost-5-en-3β,26-diol-3-O-α-l-rhamnopyrano syl-(1 → 2)-β-d-glucopyranoside 1 and (25R)-22-O-methyl-furost-5-en-3β,26-diol-3-O-α-l-r
- Wang, Haixing,Su, Fuqin,Zhou, Liang,Chen, Xiaoguang,Lei, Pingsheng
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Read Online
- Microwave irradiation for accelerating the synthesis of thioglycosides
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A simple and efficient procedure for the synthesis of thioglycosides has been achieved from the reaction of glycosylisothiouronium salts with alkyl or heteroaryl halides under microwave irradiation, in much shorter times and in yields comparable with conventional methods. Copyright Taylor & Francis Group, LLC.
- El Ashry,Awad,Hamid, H. M. Abdel,Atta
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Read Online
- Synthesis of S-linked glycoconjugates and S-disaccharides by thiol-ene coupling reaction of enoses
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Free-radical hydrothiolation of the endocyclic double bond of enoses is reported. Reaction between 2-acetoxy-D-glucal and a range of thiols including amino acid, peptide, glycosyl thiols, and sugars with primary or secondary thiol functions gave S-linked α-glucoconjugates and S-disaccharides with full regio- and stereoselectivity. Addition of glycosyl thiols to a 2,3-unsaturated glycoside also proceeded with good selectivity and afforded a series of 3-deoxy-S-disaccharides.
- Lázár, László,Csávás, Magdolna,Herczeg, Mihály,Herczegh, Pál,Borbás, Anikó
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- An improved method for the preparation of some ethyl 1-thioglycosides
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Ethyl 1-thioglycosides were prepared in almost quantitative yield from sugar peracetates in 3:2 chloroform-ether, with boron trifluoride diethyl etherate as catalyst. D-Galactose, D-glucose, and 2-deoxy-2-phthalimido-D-glucose yielded almost exclusively β anomers, whereas L-rhamnose and D-mannose resulted predominantly in the α anomers.
- Das, Saibal Kumar,Roy, Nirmolendu
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- A Sugar-Based Gelator for Marine Oil-Spill Recovery
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Marine oil spills constitute an environmental disaster with severe adverse effects on the economy and ecosystem. Phase-selective organogelators (PSOGs), molecules that can congeal oil selectively from oil–water mixtures, have been proposed to be useful for oil-spill recovery. However, a major drawback lies in the mode of application of the PSOG to an oil spill spread over a large area. The proposed method of using carrier solvents is impractical for various reasons. Direct application of the PSOG as a solid, although it would be ideal, is unknown, presumably owing to poor dispersion of the solid through the oil. We have designed five cheap and easy-to-make glucose-derived PSOGs that disperse in the oil phase uniformly when applied as a fine powder. These gelators were shown to selectively congeal many oils, including crude oil, from oil–water mixtures to form stable gels, which is an essential property for efficient oil-spill recovery. We have demonstrated that these PSOGs can be applied aerially as a solid powder onto a mixture of crude oil and sea water and the congealed oil can then be scooped out. Our innovative mode of application and low cost of the PSOG offers a practical solution to oil-spill recovery.
- Vibhute, Amol M.,Muvvala, Venkatanarayana,Sureshan, Kana M.
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Read Online
- Concise Synthesis of 1-Thioalkyl Glycoside Donors by Reaction of Per-O-acetylated Sugars with Sodium Alkanethiolates under Solvent-Free Conditions
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A relatively green method for synthesizing 1-thioalkyl glycosides has been developed, where sodium alkanethiolates were used to react with per-O-acetylated sugars instead of odorous alkyl mercaptans in the presence of BF3·Et2O without the use of solvents under mild conditions. Furthermore, we found that 1,2-trans-β-thioglycosides can be converted into corresponding 1,2-cis-α-thioglycosides in the presence of trifluoromethanesulfonic acid in nonpolar solvents under mild conditions. This provides a simple and efficient new approach for synthesizing challenging 1,2-cis-α-thioglycosides.
- Feng, Guang-Jing,Luo, Tao,Guo, Yang-Fan,Liu, Chun-Yang,Dong, Hai
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p. 3638 - 3646
(2022/02/07)
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- Beta-D-glucose short-chain fatty acid ester compound as well as preparation method and application thereof
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The invention discloses a beta-D-glucose short-chain fatty acid ester compound as well as a preparation method and application thereof, and belongs to the technical field of organic synthesis. The compound is a compound shown as a formula I, or a stereoisomer, a pharmaceutically acceptable salt, a solvate or a prodrug of the compound shown as the formula I. The formula is as shown in the description, wherein R is a methyl group, an ethyl group, a propyl group, a propylene group, an isopropylidene group, a butyl group, a butylidene group, an isobutylidene group, an amyl group, a pentylidene group or an isoamylidene group. The compound has potential prevention and treatment effects on diabetes, hyperlipidemia, atherosclerosis, Alzheimer's disease, cardiovascular and cerebrovascular diseases,inflammation, tumors and depression.
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Paragraph 0033; 0057; 0059
(2021/04/03)
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- A versatile approach to the synthesis of glycans containing mannuronic acid residues
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Reported herein is a new method for a highly effective synthesis of β-glycosides from mannuronic acid donors equipped with the 3-O-picoloyl group. The stereocontrol of glycosylations was achieved by means of the H-bond-mediated aglycone delivery (HAD). The method was utilized for the synthesis of a tetrasaccharide linkedviaβ-(1 → 3)-mannuronic linkages. We have also investigated 3,6-lactonized glycosyl donors that provided moderate to high β-manno stereoselectivity in glycosylations. A method to achieve complete α-manno stereoselectivity with mannuronic acid donors equipped with 3-O-benzoyl group is also reported.
- Alex, Catherine,Visansirikul, Satsawat,Demchenko, Alexei V.
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supporting information
p. 2731 - 2743
(2021/04/07)
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- Developing a library of mannose-based mono-and disaccharides: A general chemoenzymatic approach to monohydroxylated building blocks
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Regioselective deprotection of acetylated mannose-based mono-and disaccharides differently functionalized in anomeric position was achieved by enzymatic hydrolysis. Candida rugosa lipase (CRL) and Bacillus pumilus acetyl xylan esterase (AXE) were immobilized on octyl-Sepharose and glyoxyl-agarose, respectively. The regioselectivity of the biocatalysts was affected by the sugar structure and functionalization in anomeric position. Generally, CRL was able to catalyze regioselective deprotection of acetylated monosaccharides in C6 position. When acetylated disaccharides were used as substrates, AXE exhibited a marked preference for the C2, or C6 position when C2 was involved in the glycosidic bond. By selecting the best enzyme for each substrate in terms of activity and regioselectivity, we prepared a small library of differently monohydroxylated building blocks that could be used as intermediates for the synthesis of mannosylated glycoconjugate vaccines targeting mannose receptors of antigen presenting cells.
- Bavaro, Teodora,Marzatico, Sara,Recca, Teresa,Robescu, Marina Simona,Tanzi, Lisa,Terreni, Marco,Zhang, Yongmin
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- Chemical glucosylation of pyridoxine
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The chemical synthesis of pyridoxine-5′-β-D-glucoside (5′-β-PNG) was investigated using various glucoside donors and promoters. Hereby, the combination of α4,3-O-isopropylidene pyridoxine, glucose vested with different leaving and protecting groups and the application of stoichiometric amounts of different promoters was examined with regards to the preparation of the twofold protected PNG. Best results were obtained with 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl fluoride and boron trifluoride etherate (2.0 eq.) as promoter at 0 °C (59%). The deprotection was accomplished stepwise with potassium/sodium hydroxide in acetonitrile/water followed by acid hydrolysis with formic acid resulting in the chemical synthesis of 5′-β-PNG.
- Bachmann, Thomas,Rychlik, Michael
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supporting information
(2020/02/13)
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- Triflic acid-mediated synthesis of thioglycosides
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An efficient synthesis of thioglycosides from per-acetates in the presence of triflic acid is described. The developed protocol features high reaction rates and product yields. Some reactive sugar series give high efficiency in the presence of sub-stoichiometric trifluoromethanesulfonic acid (TfOH) in contrast to other known protocols that require multiple equivalents of Lewis acids to reach high conversion rates.
- Escopy, Samira,Singh, Yashapal,Demchenko, Alexei V.
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supporting information
p. 8379 - 8383
(2019/09/30)
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- Visible Light Enables Aerobic Iodine Catalyzed Glycosylation
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A versatile protocol for light induced catalytic activation of thioglycosides using iodine as an inexpensive and readily available photocatalyst was developed. Oxygen serves as a green and cost-efficient terminal oxidant and irradiation is performed with a common household LED-bulb. The scope of this glycosylation protocol was investigated in the synthesis of O-glycosides with yields up to 95 %.
- Krumb, Matthias,Lucas, Tobias,Opatz, Till
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supporting information
p. 4517 - 4521
(2019/08/06)
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- Preparation method of clostridium bolteae surface capsular polysaccharide structure derivative
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The invention discloses a preparation method of a clostridium bolteae surface capsular polysaccharide structure derivative and belongs to the field of sugar chemistry. The preparation method comprisesthe following steps: taking glucose as a glycosyl donor to obtain a target beta-glycosidic bond; then successfully synthesizing a disaccharide building block through an oxidization-reduction glucoseC-2 site method; then synthesizing a target oligosaccharide structure which takes the disaccharide building block as a repeating unit, such as the gram-positive bacterium surface capsular polysaccharide structure derivative [arrow3]-alpha-D-Manp-(1arrow4)-beta-D-Rhap-(1arrow]5-Linker. A reducing end of decaose is connected with a connecting arm and is used for connecting protein to form a glycoconjugate for carrying out immunology researches. The method provided by the invention has the advantages of simplicity, time saving, labor saving and low cost; the obtained clostridium bolteae surface capsular polysaccharide structure derivative is possibly used for developing and preparing medicine related to autism.
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Paragraph 0059; 0069-0071
(2018/08/28)
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- Rapid Synthesis of l-Idosyl Glycosyl Donors from α-Thioglucosides for the Preparation of Heparin Disaccharides
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A new methodology for the synthesis of the most challenging heparin building block has been developed. Orthogonally protected l-idosyl glycosyl donors were prepared by C5 epimerization of the corresponding thioglucosides using the hydroboration/oxidation method followed by a 4,6-acetal formation. The α-anomeric configuration was crucial, and the bulky C4 substituent was advantageous for the high l-ido diastereoselectivity. The 4,6-arylmethylene group proved to be a directing element in glycosylation, whereby stereoselective α-idosylation could be achieved by using idosyl donors without a C-2 participating group.
- Herczeg, Mihály,Demeter, Fruzsina,Balogh, Tímea,Kelemen, Viktor,Borbás, Anikó
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p. 3312 - 3316
(2018/07/13)
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- An Empirical Understanding of the Glycosylation Reaction
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Reliable glycosylation reactions that allow for the stereo- and regioselective installation of glycosidic linkages are paramount to the chemical synthesis of glycan chains. The stereoselectivity of glycosylations is exceedingly difficult to control due to the reaction's high degree of sensitivity and its shifting, simultaneous mechanistic pathways that are controlled by variables of unknown degree of influence, dominance, or interdependency. An automated platform was devised to quickly, reproducibly, and systematically screen glycosylations and thereby address this fundamental problem. Thirteen variables were investigated in as isolated a manner as possible, to identify and quantify inherent preferences of electrophilic glycosylating agents (glycosyl donors) and nucleophiles (glycosyl acceptors). Ways to enhance, suppress, or even override these preferences using judicious environmental conditions were discovered. Glycosylations involving two specific partners can be tuned to produce either 11:1 selectivity of one stereoisomer or 9:1 of the other by merely changing the reaction conditions.
- Chatterjee, Sourav,Moon, Sooyeon,Hentschel, Felix,Gilmore, Kerry,Seeberger, Peter H.
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supporting information
p. 11942 - 11953
(2018/09/27)
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- A NOVEL SYNTHETIC NEISSERIA MENINGITIDIS SEROGROUP A OLIGOMER AND PROCESS FOR SYNTHESIZING THEREOF
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The present invention relates to novel synthetic Neisseria meningitidis Serogroup A (hereinafter MenA) capsular polysaccharide repeating unit oligomer and a process for synthesizing said synthetic MenA capsular polysaccharide repeating unit oligomer. More specifically, the present invention relates to the chemical synthesis of the tetramer of MenA capsular polysaccharide repeating unit capable of being used as a candidate in the development of semisynthetic or fully synthetic conjugate vaccines as monovalent or as a part of combination vaccines against Meningococcal serogroup A bacterial infection.
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Page/Page column 14; 17
(2018/10/19)
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- Chemical Synthesis of Modified Hyaluronic Acid Disaccharides
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Herein we report a chemical synthesis towards new modified hyaluronic acid oligomers by using only commercially available d-glucose and d-glucosamine hydrochloride. The various protected hyaluronic acid disaccharides were synthesized bearing new functional groups at C-6 of the β-d-glucuronic acid moiety with a view to structure-related biological activity tests. The orthogonal protecting group pattern allows ready access to the corresponding higher oligomers. Also, 1H NMR studies of the new derivatives demonstrated the effect of the various functional groups on the intramolecular electronic environment.
- Mende, Marco,Nieger, Martin,Br?se, Stefan
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p. 12283 - 12296
(2017/09/14)
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- Urea–hydrogen peroxide prompted the selective and controlled oxidation of thioglycosides into sulfoxides and sulfones
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A practical method for the selective and controlled oxidation of thioglycosides to corresponding glycosyl sulfoxides and sulfones is reported using urea–hydrogen peroxide (UHP). A wide range of glycosyl sulfoxides are selectively achieved using 1.5 equiv of UHP at 60 °C while corresponding sulfones are achieved using 2.5 equiv of UHP at 80 °C in acetic acid. Remarkably, oxidation susceptible olefin functional groups were found to be stable during the oxidation of sulfide.
- Singh, Adesh Kumar,Tiwari, Varsha,Mishra, Kunj Bihari,Gupta, Surabhi,Kandasamy, Jeyakumar
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supporting information
p. 1139 - 1144
(2017/06/20)
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- Synthesis and binding affinity analysis of α1-2- and α1-6-O/S-linked dimannosides for the elucidation of sulfur in glycosidic bonds using quartz crystal microbalance sensors
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The role of sulfur in glycosidic bonds has been evaluated using quartz crystal microbalance methodology. Synthetic routes towards α1-2- and α1-6-linked dimannosides with S- or O-glycosidic bonds have been developed, and the recognition properties assessed in competition binding assays with the cognate lectin concanavalin A. Mannose-presenting QCM sensors were produced using photoinitiated, nitrene-mediated immobilization methods, and the subsequent binding study was performed in an automated flow-through instrumentation, and correlated with data from isothermal titration calorimetry. The recorded Kd-values corresponded well with reported binding affinities for the O-linked dimannosides with affinities for the α1-2-linked dimannosides in the lower micromolar range. The S-linked analogs showed slightly disparate effects, where the α1-6-linked analog showed weaker affinity than the O-linked dimannoside, as well as positive apparent cooperativity, whereas the α1-2-analog displayed very similar binding compared to the O-linked structure.
- Norberg, Oscar,Wu, Bin,Thota, Niranjan,Ge, Jian-Tao,Fauquet, Germain,Saur, Ann-Kathrin,Aastrup, Teodor,Dong, Hai,Yan, Mingdi,Ramstr?m, Olof
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supporting information
p. 35 - 42
(2017/10/25)
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- Dehydrative Thioglycosylation of 1-Hydroxyl Glycosides Catalyzed by In Situ-Generated AlI3
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Thioglycosylation of 1-hydroxyl glycosides catalyzed by in situ-generated AlI3 from elemental aluminium and molecular iodine has been developed. This method provides an alternative route to access anomeric thioglycosides without the use of hazard Lewis acidic activators or per-modified activated thiol sources. The major advantages of this dehydrative procedure are environmental friendly, ease of operation, high anomeric diastereoselectivity, and mild reaction conditions.
- Weng, Shiue-Shien,Hsieh, Kun-Yi,Zeng, Zih-Jian
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p. 464 - 473
(2017/05/19)
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- Oxidative activation of C-S bonds with an electropositive nitrogen promoter enables orthogonal glycosylation of alkyl over phenyl thioglycosides
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A method for the selective activation of thioglycosides that uses the N+-thiophilic reagent Omesitylenesulfonylhydroxylamine (MSH) as a promoter is presented. The reaction proceeds via anomeric mesitylensulfonate intermediates, which could be isolated and fully characterized by placing a fluorine atom at the C2 position. In the presence of a soft Lewis acid, glycosylation reaction proceeds at ambient temperature with good yields. It is further demonstrated that it is possible to orthogonally activate S-ethyl in the presence of S-phenyl donors, enabling the design of sequential glycosylation strategies.
- Kitowski, Annabel,Jiménez-Moreno, Ester,Salvadó, Míriam,Mestre, Jordi,Castillón, Sergio,Jiménez-Osés, Gonzalo,Boutureira, Omar,Bernardes, Gon?alo J.L.
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supporting information
p. 5490 - 5493
(2017/11/07)
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- Efficient one-pot per-: O -acetylation-thioglycosidation of native sugars, 4,6- O -arylidenation and one-pot 4,6- O -benzylidenation-acetylation of S -/ O -glycosides catalyzed by Mg(OTf)2
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A sequential one-pot per-O-acetylation-S-/O-glycosidation of native mono and disaccharides under solvent free conditions using 0.5 mole% of Mg(OTf)2 as a non-hygroscopic, recyclable catalyst is reported. Regioselective 4,6-O-arylidenation of glycosides and thioglycosides with benzaldehyde or p-methoxybenzaldehyde dimethyl acetal is catalyzed by 10 mole% of Mg(OTf)2 to produce the corresponding 4,6-O-arylidenated product in high yields. Mg(OTf)2 can also mediate sequential one-pot benzylidenation-acetylation of mono and disaccharide based glycosides and thioglycosides in high yield.
- Mukherjee, Mana Mohan,Basu, Nabamita,Chaudhury, Aritra,Ghosh, Rina
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p. 109301 - 109314
(2016/11/30)
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- Exploring glycosylation reactions under continuous-flow conditions
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The industrial development of carbohydrate-based drugs is greatly thwarted by the typical challenges inherent in oligosaccharide synthesis. The practical advantages of continuous-flow synthesis in microreactors (high reproducibility, easy scalability, and fast reaction optimization) may offer an effective support to make carbohydrates more attractive targets for drug-discovery processes. Here we report a systematic exploration of the glycosylation reaction carried out under microfluidic conditions. Trichloroacetimidates and thioglycosides have been investigated as glycosyl donors, using both primary and secondary acceptors. Each microfluidic glycosylation has been compared with the corresponding batch reaction, in order to highlight advantages and drawbacks of microreactors technology. As a significant example of multistep continuous-flow synthesis, we also describe the preparation of a trisaccharide by means of two consecutive glycosylations performed in interconnected microreactors.
- Cancogni, Damiano,Lay, Luigi
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supporting information
p. 2873 - 2878
(2015/01/16)
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- Systematic study on free radical hydrothiolation of unsaturated monosaccharide derivatives with exo- and endocyclic double bonds
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Exo- and endocyclic double bonds of glycals and terminal double bonds of enoses were reacted with various thiols by irradiation with UV light in the presence of a cleavable photoinitiator. The photoinduced radical-mediated hydrothiolation reactions showed highly varying overall conversions depending not only on the substitution pattern and electron-density of the double bond but also on the nature and substitution pattern of the thiol partner. Out of the applied thiols thiophenol, producing the highly stabilized thiyl radical, exhibited the lowest reactivity toward each type of alkene. In most cases, the hydrothiolations took place with full regio- and stereoselectivities. Successful addition of 1,2:3,4-di-O-isopropylidene-6-thio-α-d-galactopyranose to a 2,3-unsaturated N-acetylneuraminic acid derivative, providing a (3 → 6)-S-linked pseudodisaccharide, demonstrated that the endocyclic double bond of Neu5Ac-2-ene, bearing an electron-withdrawing substituent, shows sufficient reactivity in the photoinduced thiol-ene coupling reaction.
- Lazar, Laszlo,Csavas, Magdolna,Hadhazi, Adam,Herczeg, Mihaly,Toth, Marietta,Somsak, Laszlo,Barna, Terezia,Herczegh, Pal,Borbas, Aniko
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p. 5339 - 5350
(2013/08/23)
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- Synthesis of 6-sulfonatomethyl thioglycosides by nucleophilic substitution: Methods to prevent 1→6 anomeric group migration of thioglycoside 6-o-triflates
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Introduction of a sulfonatomethyl moiety into the primary position of thioglycosides by nucleophilic displacement of the corresponding 6-O-triflate is described. The 1→6 migration of the anomeric group, which inevitably occurs through a bicyclic sulfonium ion intermediate, from conformationally flexible β-thioglycosides was prevented by using an α-thioglycoside or conformationally locked β-thioglycoside as the starting material. The thioglycoside 6-sulfonic acids showed excellent α-selectivity during synthesis of uronic acid containing heparinoid trisaccharides. Two routes to prepare C6-sulfonatomethyl thioglucosides by displacement of a 6-O-triflate moiety are reported. The undesired participation of the β-thio aglycon is prevented by changing the anomeric configuration or by locking the pyranose ring. The 6-sulfonatomethyl donors show excellent α-selectivities but significantly different reactivities during the synthesis of heparinoid trisaccharides. Copyright
- Herczeg, Mihaly,Mezo, Erika,Eszenyi, Daniel,Lazar, Laszlo,Csavas, Magdolna,Bereczki, Ilona,Antus, Sandor,Borbas, Aniko
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p. 5570 - 5573
(2013/09/12)
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- Development of fully and partially protected fucosyl donors for oligosaccharide synthesis
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The use of fully and partially tert-butyldimethylsilyl (TBDMS) protected fucose thioglycosides as glycosyl donors for oligosaccharide synthesis is described. Both the trisilyl- and disilyl-protected thioglycoside donors were prepared, and their reactivity under a range of activation conditions was investigated. Both silyl-protected donors were found to give good yields of the desired α products and the silyl protecting groups could be removed in the presence of unsaturated bonds. The disilyl-protected donor was found to behave as an efficient, partially protected glycosyl donor. The synthetic scope and limitations of these new donors is presented. Both donors were applied to the synthesis of a Lewis X trisaccharide displaying a propargyl group at the anomeric position. It was determined that the additional steric bulk of the TBDMS group inferred unusual reactivity on these fucosyl donors.
- Daly, Robin,McCabe, Thomas,Scanlan, Eoin M.
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p. 1080 - 1090
(2013/03/29)
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- High-yield total synthesis of (-)-strictinin through intramolecular coupling of gallates
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This paper describes a total synthesis of (-)-strictinin, an ellagitannin that is 1-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl (HHDP)-β-d-glucose. In the study, total efficiency of the synthesis was improved to produce a 78% overall yield in 13 steps from d-glucose. In the synthesis, formation of the 4,6-(S)-HHDP bridge including the 11-membered bislactone ring was a key step, in which intramolecular aryl-aryl coupling was adopted. The coupling was oxidatively induced by CuCl2-n-BuNH2 with perfect control of the axial chirality, and the reaction conditions of this coupling were optimized thoroughly to achieve the quantitative formation of the bridge.
- Michihata, Naoki,Kaneko, Yuki,Kasai, Yusuke,Tanigawa, Kotaro,Hirokane, Tsukasa,Higasa, Sho,Yamada, Hidetoshi
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p. 4319 - 4328
(2013/06/27)
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- Polymethylhydrosiloxane (PMHS): A convenient option for synthetic applications of the iodine/silane combined reagent - Straightforward entries to 2-hydroxyglycals and useful building-blocks of glucuronic acid and glucosamine
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Polymethylhydrosiloxane (PMHS) proved to be a practically convenient alternative to triethylsilane in a large set of synthetic elaborations entailing the quick generation of glycosyl iodides with a iodine/silane combined reagent. In addition, the scope of this combined reagent was expanded to the especially fast generation of 2-acetoxyglycals, and the rapid synthesis of useful building-blocks of D-glucuronic acids and D-glucosamine. All the synthetic targets were obtained in especially short times either via one-pot procedures or through experimental sequences devoid of laborious chromatographical purifications of intermediates. Polymethylhydrosiloxane (PMHS) is a practically convenient alternative to triethylsilane in a large set of synthetic elaborations entailing the quick generation of glycosyl iodides with a iodine/silane combined reagent. Copyright
- Giordano, Maddalena,Iadonisi, Alfonso
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p. 125 - 131
(2013/02/25)
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- 'Naked' and hydrated conformers of the conserved core pentasaccharide of N-linked glycoproteins and its building blocks
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N-glycosylation of eukaryotic proteins is widespread and vital to survival. The pentasaccharide unit -Man3GlcNAc2- lies at the protein-junction core of all oligosaccharides attached to asparagine side chains during this process. Although its absolute conservation implies an indispensable role, associated perhaps with its structure, its unbiased conformation and the potential modulating role of solvation are unknown; both have now been explored through a combination of synthesis, laser spectroscopy, and computation. The proximal -GlcNAc-GlcNAc- unit acts as a rigid rod, while the central, and unusual, -Man-β-1,4-GlcNAc- linkage is more flexible and is modulated by the distal Man-α-1,3- and Man-α-1,6- branching units. Solvation stiffens the 'rod' but leaves the distal residues flexible, through a β-Man pivot, ensuring anchored projection from the protein shell while allowing flexible interaction of the distal portion of N-glycosylation with bulk water and biomolecular assemblies.
- Barry, Conor S.,Cocinero, Emilio J.,Carcabal, Pierre,Gamblin, David P.,Stanca-Kaposta, E. Cristina,Remmert, Sarah M.,Fernandez-Alonso, Maria C.,Rudic, Svemir,Simons, John P.,Davis, Benjamin G.
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supporting information
p. 16895 - 16903
(2013/12/04)
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- Preparation of α- And β-D-glucoseptanose pentaacetates
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The α- and β-d-glucoseptanose pentaacetates have been prepared by treatment of ethyl 1-thio-β-d-glucoseptanoside tetraacetate with mercury(II) acetate in acetic acid. The solid state structure of the β-isomer has been determined by X-ray diffraction.
- Bhadbhade, Mohan,Craig, Donald C.,Ng, Clarence J.,Odier, Leon,Stevens, John D.
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- GLYCOMIMETIC COMPOUNDS AND METHODS TO INHIBIT INFECTION BY HIV
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Compounds, compositions and methods are provided for use to inhibit infection by human immunodeficiency virus (HIV). More specifically, the present invention relates to glycomimetic compounds that inhibit HIV infection, and uses thereof.
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Page/Page column 8; sheet 3
(2011/10/19)
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- Diastereoselective thioglycosylation of peracetylated glycosides catalyzed by in situ generated iron(III) iodide from elemental iodine and iron
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A facile in situ preparation of Fe(III) iodide from cheap, abundant elemental iodine and iron metal served as an efficient catalyst for the thioglycosylation of peracetylated glycosides with various alkyl and aryl mercaptans. Due to neighboring participation, the anomerically pure β-thioglycosides were obtained in good to high yields with exclusive diastereocontrol.
- Weng, Shiue-Shien
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supporting information; experimental part
p. 6414 - 6417
(2010/02/28)
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- Preparation of Thiosugars and Their Use
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A process for the preparation of a thiosaccharide represented by Saccharide-S-H wherein Saccharide comprises at least 4 sugar units, comprises subjecting a corresponding compound of the formula (P)Saccharide-S-(P) wherein (P) represents an O- or S-protecting group(s), to Birch reduction.
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Page/Page column 7; 18
(2009/07/18)
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- Solvent-free synthesis of thioglycosides by ball milling
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Thioglycosides have been prepared in excellent yields by three different routes from a range of readily available glycosyl halides under solvent-free conditions employing a planetary ball mill.
- Ramrao Patil, Premanand,Ravindranathan Kartha
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experimental part
p. 953 - 956
(2010/04/23)
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- Involvement of the S-aglycon in the conformational preferences of thioglucosides
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The conformational preferences of two series of alkyl β-d-thioglucopyranosides in solution were investigated by NMR and CD. The rotamer populations of the hydroxymethyl group were found to depend on the structural nature of the S-aglycon. The population of the gt rotamer increased and that of the gg rotamer decreased as the alkyl group attached to the S atom increased in size. These rotamer populations have a linear correlation with the Taft' steric parameters, the nS s(-) σC s(-) O* exo-anomeric interaction may express these rotational preferences. Comparative analysis of the hydroxymethyl populations between alkyl O- and S-glucosides revealed identical or slightly higher gt and smaller gg populations for the latter compounds.
- Sanhueza, Carlos A.,Dorta, Rosa L.,Vazquez, Jesus T.
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p. 258 - 264
(2008/09/19)
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- Novel approaches for the synthesis and activation of thio- and selenoglycoside donors
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(Chemical Equation Presented) Alkyl thio-, phenyl seleno-, and phenyl thioglycosides can be prepared through short synthetic sequences based on the generation of glycosyl iodides as versatile intermediates. In addition, a novel cheap combined system (stoichiometric NBS and catalytic Bi(OTf)3) has been developed for rapid and efficient activation of a wide variety of thio- and selenoglycoside donors.
- Valerio, Silvia,Iadonisi, Alfonso,Adinolfi, Matteo,Ravida, Alessandra
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p. 6097 - 6106
(2008/02/09)
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- Method for synthesis of beta glucans
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The invention provides a method for forming P-glucoside linkages in carbohydrate polymers, particularly synthetic glucan molecules, by attaching a protecting group to the C2 position of a glucoside donor. The protecting group of the invention stabilizes t
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Page/Page column 9
(2010/10/20)
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- A generalized procedure for the one-pot preparation of glycosyl azides and thioglycosides directly from unprotected reducing sugars under phase-transfer reaction conditions
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Per-O-acetylated glycosyl azides and thioglycosides were prepared in excellent yield directly from unprotected reducing sugars through in situ generation of per-O-acetylated glycosyl bromides by a generalized one-pot procedure under phase-transfer conditions. Stereoselective products were formed with complete inversion at the anomeric centers of the glycosyl bromides to provide a general high-yielding procedure for the preparation of 1,2-trans-glycosyl azides and thioglycosides. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Kumar, Rishi,Tiwari, Pallavi,Maulik, Prakas R.,Misra, Anup K.
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- Highly diastereoselective thioglycosylation of functionalized peracetylated glycosides catalyzed by MoO2Cl2
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Among 18 oxometallic species, MoO2Cl2 was found to be the most reactive in catalytic thioglycosylation of O-acetylated glycosides with functionalized thiols in CH2Cl2, leading cleanly to 1,2-trans-thioglycosides with exclusive diastereocontrol. The new catalytic protocol is applicable to a monoglycoside building block and β-(1→6)-S-linked-thiodisaccharide synthesis.
- Weng, Shiue-Shien,Lin, Yow-Dzer,Chen, Chien-Tien
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p. 5633 - 5636
(2007/10/03)
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- Acylation of carbohydrates over Al2O3: Preparation of partially and fully acylated carbohydrate derivatives and acetylated glycosyl chlorides
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Selective and per-O-acylation of carbohydrate derivatives using acyl chlorides and Al2O3, a solid support reagent, is reported. This protocol does not require the addition of any base or activator. This methodology has been further extended to the selective acylation of carbohydrate diols and the one-pot preparation of acetylated glycosyl chlorides direct from free reducing sugars. The yields obtained in most of the cases are excellent.
- Tiwari, Pallavi,Misra, Anup Kumar
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p. 339 - 350
(2007/10/03)
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- One-pot synthesis of per-O-acetylated thioglycosides from unprotected reducing sugars
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A sequential per-O-acetylation and thioglycosidation of unprotected reducing sugars using a stoichiometric quantity of acetic anhydride and alkyl- or arylthiols is reported. These reactions, which are catalyzed by BF 3·OEt2, together constitute an efficient one-pot method for the synthesis of acetylated thioglycosides.
- Agnihotri, Geetanjali,Tiwari, Pallavi,Misra, Anup Kumar
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p. 1393 - 1396
(2007/10/03)
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- HClO4-SiO2 catalyzed per-O-acetylation of carbohydrates
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An efficient per-O-acetylation of carbohydrates catalyzed by HClO 4-SiO2 is reported using a stoichiometric quantity of acetic anhydride avoiding the use of pyridine and excess acetic anhydride under solvent-free conditions.
- Misra, Anup Kumar,Tiwari, Pallavi,Madhusudan, Soni Kamlesh
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p. 325 - 329
(2007/10/03)
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- Efficient acetylation of carbohydrates promoted by imidazole
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An efficient per-O-acetylation of carbohydrate derivatives and unprotected reducing sugars promoted by imidazole is reported. The reaction conditions have been successfully employed to acetylate carbohydrate derivatives containing acid-susceptible functional groups. In most of the cases the yields obtained were excellent. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Tiwari, Pallavi,Kumar, Rishi,Maulik, Prakas R.,Misra, Anup Kumar
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p. 4265 - 4270
(2007/10/03)
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- Streamlined synthesis of per-O-acetylated sugars, glycosyl iodides, or thioglycosides from unprotected reducing sugars
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Solvent-free per-O-acetylation of sugars with stoichiometric acetic anhydride and catalytic iodine proceeds in high yield (90-99%) to give exclusively pyranose products as anomeric mixtures. Without workup, subsequent anomeric substitution employing iodine in the presence of hexamethyldisilane (i.e., TMS-I generated in situ) gives the corresponding glycosyl iodides in 75-95% isolated yield. Alternatively, and without workup, further treatment with dimethyl disulfide or thiol (ethanethiol or thiocresol) gives anomerically pure thioglycosides in more than 75% overall yield.
- Mukhopadhyay, Balaram,Kartha, K.P. Ravindranathan,Russell, David A.,Field, Robert A.
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p. 7758 - 7760
(2007/10/03)
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- A mild and convenient indium(III) chloride-catalyzed synthesis of thioglycosides
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The efficiency of glycosidation reactions generally involves a high chemical yield, as well as high/complete stereo- and regioselectivity. All these depend on the compatibility of the reactivity of glycosyl donors and acceptors. Among glycosyl donors, thi
- Das, Saibal Kumar,Roy, Joyita,Reddy, Kalusani Anantha,Abbineni, Chandrasekhar
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p. 2237 - 2240
(2007/10/03)
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- Can preferential β-mannopyranoside formation with 4,6-O-benzylidene protected mannopyranosyl sulfoxides be reached with trichloroacetimidates?
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Studies with 3-O-allyl-2-O-benzyl-4,6-O-benzylidene-α-D-mannopyranosyl sulfoxide (3d) and the corresponding trichloroacetimidate (4) as glycosyl donors and various acceptors (A-F) led under similar reaction conditions to similar glycosylation results, i.e. mainly or exclusively the β-anomers of glycosides 5dA-5dF could be obtained. Thus, the versatile building block 5dA for N-glycan synthesis is readily available. For the activation of the sulfoxide leaving group, one equivalent of Tf2O and two equivalents of DTBMP are required, whereas for trichloroacetimidate activation catalytic amounts of TMSOTf are sufficient; hence, the trichloroacetimidate based procedure is very convenient. Various parameters were modified in the reaction of 4 with A (catalyst concentration, configuration of 4, size of the 2-O-protective group, solvent), thus, a proposal for the reaction course was derived. (C) 2000 Elsevier Science Ltd.
- Weingart,Schmidt
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p. 8753 - 8758
(2007/10/03)
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- Synthesis of a group of diosgenyl saponins with combined use of glycosyl trichloroacetimidate and thioglycoside donors
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With the combined use of glycosyl trichloroacetimidates and thioglycosides, a group of natural diosgenyl saponins (1-6) are efficiently synthesized, in either a stepwise or a 'one-pot' manner. The trichloroacetimidate is employed as an efficient temporary hydroxy protecting group in glycosylation with the glycosyl trichloroacetimidate. The intermolecular alkylthio-group transfer is demonstrated to be a common side-reaction during glycosylation with thioglycosides. The Royal Society of Chemistry 2000.
- Yu, Hai,Yu, Biao,Wu, Xiangyang,Hui, Yongzheng,Han, Xiuwen
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p. 1445 - 1453
(2007/10/03)
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- Iodine and its interhalogen compounds: Versatile reagents in carbohydrate chemistry v. synthesis of 1,2-trans-linked 1-thioglycosides from the per-o-acetylated glycoses
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Treatment of per-O-acetylated mono- and di-saccharides with (alkyl/arylthio)trimethylsilane and iodine at ambient temperature results in the formation of the corresponding 1,2-trans-1-thioglycosides in very high yield. In the case of higher boiling thiols such as ethanethiol, the reaction can be effectively carried out in the presence of the thiol itself instead of the silylated derivative, but the reaction is not stereospecific. Moreover, in the latter reactions a portion of the starting material remains unchanged even on prolonged reaction. With β-D-glucose pentaacetate (11) as the starting material, its epimerisation occurred during the reaction and therefore the recovered starting material was of α-D-configuration. In addition, the methyl disulphide-hexamethyldisilane system has been found to serve as an effective and cheaper alternative to the expensive (methylthio)-trimethylsilane.
- Kartha, K. P. Ravindranathan,Field, Robert A.
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p. 693 - 702
(2007/10/03)
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- Regioselective Lipase-catalysed acylation of 4,6-O-benzylidene-α- and - β-D-pyranoside derivatives displaying a range of anomeric substituents
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The application of Lipase enzymes to effect regioselective C-3-O- acylation of 4,6-O-benzylidene-β-D-gluco- and -galactopyranosides displaying a range of anomeric substituents, and C-2-O-acylation of phenyl 4,6-O- benzylidene-α-D-glucopyranoside and ethyl 4,6-O-benzylidene-1-thio-α-D- glucopyranoside is reported. In particular this method has allowed introduction of a variety of acyl protecting groups at the C-3 hydroxyl group of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside 11.
- Gridley, Jonathan J.,Hacking, Andrew J.,Osborn, Helen M. I.,Spackman, David G.
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p. 14925 - 14946
(2007/10/03)
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- Regioselective lipase-catalysed acylation of 4,6-O-benzylidene-β-D-pyranoside derivatives displaying a range of anomeric substituents
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The application of lipase enzymes to effect regioselective C-3-O-acylation of 4,6-O-benzylidene-β-D-gluco- and galactopyranosides displaying a range of anomeric substituents is reported. In particular this method has allowed introduction of a variety of acyl protecting groups at the C-3 hydroxyl group of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside 9.
- Gridley, Jonathan J.,Hacking, Andrew J.,Osborn, Helen M. I.,Spackman, David G.
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p. 1397 - 1399
(2007/10/03)
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