- Direct dehydrative glycosylation catalyzed by diphenylammonium triflate
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Methods for direct dehydrative glycosylations of carbohydrate hemiacetals catalyzed by diphenylammonium triflate under microwave irradiation are described. Both armed and disarmed glycosyl-C1-hemiacetal donors were efficiently glycosylated in moderate to excellent yields without the need for any drying agents and stoichiometric additives. This method has been successfully applied to a solid-phase glycosylation.
- Hsu, Mei-Yuan,Lam, Sarah,Lin, Mei-Huei,Lin, Su-Ching,Wang, Cheng-Chung,Wu, Chia-Hui
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supporting information
(2020/03/13)
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- Photo-induced glycosylation using a diaryldisulfide as an organo-Lewis photoacid catalyst
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Photo-induced glycosylations of several acceptors with trichloroacetimidate donors using bis(2-naphthyl)disulfide as an organo-Lewis photoacid (LPA) catalyst proceeded effectively to give the corresponding glycosides in good to high yields. In addition, t
- Iibuchi, Naoto,Eto, Takahiro,Aoyagi, Manabu,Kurinami, Reiji,Sakai, Hayato,Hasobe, Taku,Takahashi, Daisuke,Toshima, Kazunobu
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supporting information
p. 851 - 855
(2020/02/15)
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- A visible light promoted O-glycosylation with glycosyl trichloroacetimidates using eosin Y as an organo photoacid
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A photoacid catalyzed O-glycosylation of alcohols with glycosyl trichloroacetimidates in the presence of commercially available phenolic photoacids, fluorescein, 4′,5′-dibromo-fluorescein, and eosin Y under visible light irradiation by blue LEDs was devel
- Li, Hongfang,Liu, Jiao,Ni, Guanghui,Wang, Haimei,Yin, Shan
-
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- Visible light promoted method for constructing O-glycoside bonds
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The invention discloses a visible light promoted method for constructing O-glycoside bonds. Glycosyl trichloroacetimidate is taken as a donor, and phenolic compounds are taken as a photocatalyst; a molecular sieve is added; and the O-glycoside bonds are g
- -
-
Paragraph 0028-0029
(2020/07/13)
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- Remote Participation during Glycosylation Reactions of Galactose Building Blocks: Direct Evidence from Cryogenic Vibrational Spectroscopy
-
The stereoselective formation of 1,2-cis-glycosidic bonds is challenging. However, 1,2-cis-selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short-lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α-selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium-type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2-cis-glycosidic bonds.
- Marianski, Mateusz,Mucha, Eike,Greis, Kim,Moon, Sooyeon,Pardo, Alonso,Kirschbaum, Carla,Thomas, Daniel A.,Meijer, Gerard,von Helden, Gert,Gilmore, Kerry,Seeberger, Peter H.,Pagel, Kevin
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supporting information
p. 6166 - 6171
(2020/03/10)
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- Gold(III)-Catalyzed Glycosylation using Phenylpropiolate Glycosides: Phenylpropiolic Acid, An Easily Separable and Reusable Leaving Group
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An efficient and operationally simple gold(III)-catalyzed glycosylation protocol was developed using newly synthesized benchtop stable phenylpropiolate glycosyl (PPG) donors. Gold(III)-catalyzed activation of PPGs proceeds well with various carbohydrate a
- Shaw, Mukta,Thakur, Rima,Kumar, Amit
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p. 589 - 605
(2019/01/14)
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- An Unexpected FeCl 3/C-Catalyzed β-Stereoselective Glycosylation in the Presence of the C(2)-Benzyl Group
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An efficient and completely β-stereoselective glycosylation that did not rely on neighboring group participation is described using 2-20 molpercent FeCl 3 /C as the catalyst and benzylated propargyl glycosides as the donors to reach yields up to 96percent under mild condition. With an octatomic-ring intermediate at the α-face of FeCl 3 /C with alkyne of propargyl glycosides, a panel of aglycones comprising aliphatic, alicyclic, unsaturated alcohols, halogenated alcohols, and phenols with different substitution were examined successfully for the exclusive β-stereoselective glycosylation reaction.
- Guo, Hong,Li, Juan,Si, Wenshuai,Tang, Jie,Tang, Tianjun,Wang, Zhongfu,Yang, Guofang,Zhang, Jianbo
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p. 2984 - 3000
(2019/07/22)
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- N-benzoylglycine/thiourea cooperative catalyzed stereoselective O-glycosidation: Activation of O-glycosyl trichloroacetimidate donors
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A new practical utility for β-stereoselective glycosylation via activation of O-glycosyl trichloroacetimidate donors using N-benzoylglycine/thiourea cooperative catalysis has been demonstrated. This method represents the first instance where amino acid derived N-benzoylglycine is used as a catalyst for O–glycosylation under mild reaction conditions at ambient temperature. NMR spectroscopy studies suggest that thiourea cocatalyst exhibit a cooperative behaviour that has a strong effect on the reaction rate, yield, and the β-selectivity.
- Dubey, Atul,Sangwan, Rekha,Mandal, Pintu Kumar
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p. 123 - 129
(2019/04/17)
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- Silver-catalyzed stereoselective formation of glycosides using glycosyl ynenoates as donors
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A silver-catalyzed glycosylation reaction employing readily accessible and stable glycosyl ynenoates is developed. This reaction is mostly high yielding and exhibits varying levels of stereoinversion at the anomeric position. Compared to established and versatile Yu's gold catalysis, this chemistry features the use of substantially cheaper AgNTf2.
- Dong, Xu,Chen, Li,Zheng, Zhitong,Ma, Xu,Luo, Zaigang,Zhang, Liming
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p. 8626 - 8629
(2018/08/06)
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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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- Stereocontrolled glycoside synthesis by activation of glycosyl sulfone donors with scandium(III) triflate
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The activation of aryl glycosyl sulfone donors has been achieved using scandium(iii) triflate and has led to the selective preparation of α-mannosides resulting from a post-glycosylation anomerization.
- Xolin, Amandine,Losa, Romain,Kaid, Aicha,Tresse, Cédric,Beau, Jean-Marie,Boyer, Fran?ois-Didier,Norsikian, Stéphanie
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p. 325 - 335
(2018/01/12)
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- Tris(pentafluorophenyl)borane-promoted stereoselective glycosylation with glycosyl trichloroacetimidates under mild conditions
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Tris(pentafluorophenyl)borane-promoted stereoselective glycosylation with trichloroacetimidate glycosyl donors is described. The reactions proceed efficiently with a wide range of acceptors, from sugar to nonsugar, under mild conditions in the presence of
- Mishra, Kunj Bihari,Singh, Adesh Kumar,Kandasamy, Jeyakumar
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p. 4204 - 4212
(2018/04/14)
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- Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors
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The glycosylation of O-glycosyl trichloroacetimidate donors using a synergistic catalytic system of electron-deficient pyridinium salts/aryl thiourea derivatives at room temperature is demonstrated. The acidity of the adduct formed by the 1, 2-addition of
- Shaw, Mukta,Kumar, Yogesh,Thakur, Rima,Kumar, Amit
-
supporting information
p. 2385 - 2395
(2017/11/16)
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- Stereocontrolled Photoinduced Glycosylation Using an Aryl Thiourea as an Organo photoacid
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Photoinduced glycosylation of alcohols with α-glucosyl trichloroacetimidates, using aryl urea and thioureas as organo photoacids, was examined under long wavelength UV (ultraviolet) irradiation. The results show, for the first time, that such glycosylatio
- Kimura, Tomoya,Eto, Takahiro,Takahashi, Daisuke,Toshima, Kazunobu
-
supporting information
p. 3190 - 3193
(2016/07/14)
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- Comparative Analysis of Fluorine-Directed Glycosylation Selectivity: Interrogating C2 [OH → F] Substitution in d- Glucose and d- Galactose
-
The influence of C2 [OH → F] substitution on the stereochemical course of chemical glycosylation was interrogated in both D-glucose and its C4 epimer D-galactose. Molecular editing at C2 and configurational inversion at C4 were simultaneously investigated
- Santschi, Nico,Gilmour, Ryan
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p. 6983 - 6987
(2015/11/16)
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- An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst: Acid-Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts
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Gold(III) chloride as catalyst for O-glycosyl trichloroacetimidate activation revealed low affinity to the glycosyl donor but high affinity to the hydroxy group of the acceptor alcohol moiety, thus leading to catalyst-acceptor adduct formation. Charge sep
- Peng, Peng,Schmidt, Richard R.
-
supporting information
p. 12653 - 12659
(2015/10/20)
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- Gold-catalysed glycosylation reaction using an easily accessible leaving group
-
Gold(iii)-catalysed glycosylation reaction has been developed by employing a new and easily accessible leaving group synthesized from ethyl cyanoacetate. Several nucleophiles like alcohols, thiols, allyltrimethylsilane, trimethylsilyl azide and triethylsilane have been reacted to make the corresponding glycosides in good yields and with marginal to excellent α-selectivity. This journal is
- Koppolu, Srinivasa Rao,Niddana, Ramana,Balamurugan, Rengarajan
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p. 5094 - 5097
(2015/05/13)
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- Strained olefin enables triflic anhydride mediated direct dehydrative glycosylation
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For the first time, we demonstrated that Tf2O mediated direct dehydrative glycosylation was possible simply with strained olefins, and other typical bases were inhibitors of this reaction. We optimized the glycosylation conditions and found tha
- Chen, Guohua,Yin, Qiang,Yin, Jian,Gu, Xiangying,Liu, Xiao,You, Qidong,Chen, Yue-Lei,Xiong, Bing,Shen, Jingkang
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supporting information
p. 9781 - 9785
(2015/01/08)
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- Photo-induced glycosylation using reusable organophotoacids
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The glycosylation reactions of glycosyl trichloroacetimidates and several alcohols using an organophotoacid as an activator under photoirradiation proceeded smoothly to give the corresponding glycosides in high yields. The organophotoacid was recovered and reused without any loss of efficiency. This journal is the Partner Organisations 2014.
- Iwata, Ryosuke,Uda, Kanjiro,Takahashi, Daisuke,Toshima, Kazunobu
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supporting information
p. 10695 - 10698
(2014/09/30)
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- Regenerative glycosylation under nucleophilic catalysis
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This article describes 3,3-difluoroxindole (HOFox)-mediated glycosylation. The uniqueness of this approach is that both the in situ synthesis of 3,3-difluoro-3H-indol-2-yl (OFox) glycosyl donors and activation thereof can be conducted in a regenerative fashion as is a typical reaction performed under nucleophilic catalysis. Only a catalytic amount of the OFox imidate donor and a Lewis acid activator are present in the reaction medium. The OFox imidate donor is constantly regenerated upon its consumption until glycosyl acceptor has reacted.
- Nigudkar, Swati S.,Stine, Keith J.,Demchenko, Alexei V.
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p. 921 - 923
(2014/02/14)
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- 1,2-trans-1-Dihydroxyboryl benzyl S-glycoside as glycosyl donor
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Activated by NBS, readily available 1,2-trans-1-dihydroxyboryl benzyl S-glycosides served as glycosyl donors and reacted with certain simple alcohol acceptors to produce pure 1,2-cis-O-glycosides in moderate yields. The boronic acid moiety was revealed es
- Liu, Xiao,Zhang, Bingbing,Gu, Xiangying,Chen, Guohua,Chen, Lin,Wang, Xin,Xiong, Bing,You, Qi-Dong,Chen, Yue-Lei,Shen, Jingkang
-
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- Cooperative catalysis in glycosidation reactions with o-glycosyl trichloroacetimidates as glycosyl donors
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Thiourea mediates cooperative glycosidation through hydrogen bonding. N,N′-Diarylthiourea as cocatalyst enforces an SN2-type acid-catalyzed glycosidation even at room temperature (see scheme; Bn=benzyl). From O-(α-glycosyl) trichloroacetimidates as glycosyl donors and various acceptors, β-glycosides are preferentially or exclusively obtained.
- Geng, Yiqun,Kumar, Amit,Faidallah, Hassan M.,Albar, Hassan A.,Mhkalid, Ibrahim A.,Schmidt, Richard R.
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p. 10089 - 10092
(2013/10/01)
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- Silicon fluorides for acid-base catalysis in glycosidations
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Adduct formation between alcohols as glycosyl acceptors and phenylsilicon trifluoride (PhSiF3) as catalyst permits acid-base-atalyzed glycosidations with O-glycosyl trichloroacetimidates as glycosyl donors. In this way, from various glycosyl do
- Kumar, Amit,Geng, Yiqun,Schmidt, Richard R.
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experimental part
p. 1489 - 1499
(2012/07/14)
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- Fluorine-directed β-galactosylation: Chemical glycosylation development by molecular editing
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Validation of the 2-fluoro substituent as an inert steering group to control chemical glycosylation is presented. A molecular editing study has revealed that the exceptional levels of diastereocontrol in glycosylation processes by using 2-fluoro-3,4,6-tri-O-benzyl glucopyranosyl trichloroacetimidate (TCA) scaffolds are a consequence of the 2R,3S,4S stereotriad. This study has also revealed that epimerization at C4, results in a substantial enhancement in β-selectivity (up to β/α 300:1). Copyright
- Durantie, Estelle,Bucher, Christoph,Gilmour, Ryan
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supporting information; experimental part
p. 8208 - 8215
(2012/08/27)
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- Dehydrative glycosylation with the Hendrickson reagent
-
The Hendrickson reagent is able to perform efficiently dehydrative glycosylation of 1-hydroxyglycosyl donors. The reaction occurs under mild conditions through an anomeric oxophosphonium intermediate detected by nuclear magnetic resonance. Further insight into the mechanism was gained by 18O labeling of anomeric OH.
- Mossotti, Matteo,Panza, Luigi
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experimental part
p. 9122 - 9126
(2011/12/16)
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- Glycoside bond formation via acid-base catalysis
-
Acid-base catalyzed glycosyl donor and then glycosyl acceptor activation with phenylboron difluoride or diphenylboron fluoride permits hydrogen bond mediated intramolecular SN2-type glycosidation in generally high anomeric selectivity.
- Kumar, Amit,Kumar, Vipin,Dere, Ravindra T.,Schmidt, Richard R.
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supporting information; experimental part
p. 3612 - 3615
(2011/09/14)
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- S-benzimidazolyl glycosides as a platform for oligosaccharide synthesis by an active-latent strategy
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Doing the Biz: The S-benzimidazolyl (SBiz) anomeric moiety is a new leaving group that can be activated for glycosylation under a variety of conditions, including metal-assisted and alkylation pathways. Application of a substituted SBiz moiety (X=anisoyl, see picture) allows active-latent and armed-disarmed types of oligosaccharide assembly. Copyright
- Hasty, Scott J.,Kleine, Matthew A.,Demchenko, Alexei V.
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p. 4197 - 4201
(2011/07/07)
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- Fluorine-directed glycosylation
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Everything's under control: A stabilizing fluorine electrostatic interaction has been exploited to control oxonium ion conformation in 2-fluoropyranose derivatives (see scheme). When matched with the inductive nature of the protecting groups, the glycosyl
- Bucher, Christoph,Gilmour, Ryan
-
supporting information; experimental part
p. 8724 - 8728
(2011/01/06)
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- IPy2BF4-mediated glycosylation and glycosyl fluoride formation
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A facile method to convert thioglycosides to glycosyl fluorides with Ipy2BF4 (py = pyridine) is presented. Alternatively, activation of thioglycosides with Ipy2BF4 in the presence of acids and glycosyl acceptors
- Huang, Kuo-Ting,Winssinger, Nicolas
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p. 1887 - 1890
(2008/02/06)
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- High-Yield Syntheses of Tetra-O-benzyl-α-D-glucopyranosyl bromide and Tetra-O-pivaloyl-α-D-glucopyranosyl bromide and their Advantage in the Koenigs-Knorr Reaction
-
Several improved approaches for the preparation of tetra-O-benzyl-α- D-glucopyranosyl bromide and tetra-O-pivaloyl-α-D-glucopyranosyl bromide are discussed. The importance of these compounds, which are useful glycosyl donors, was demonstrated by successful preparation of cholesteryl glucopyranosides in an almost neutral medium without the formation of orthoesters. In addition, accurate 1H and 13C NMR resonance assignments of the synthesized cholesteryl glycosides were performed by 2D NMR spectroscopy. Springer-Verlag 2006.
- Presser, Armin,Kunert, Olaf,Poetschger, Irmgard
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p. 365 - 374
(2007/10/03)
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- Environmentally benign β-stereoselective glycosidations of glycosyl phosphites using a reusable heterogeneous solid acid, montmorillonite K-10
-
Environmentally benign and stereoselective β-glycosidations of glycopyranosyl phosphites and alcohols using a reusable heterogeneous solid acid, montmorillonite K-10, as an activator have been developed. By these glycosidations, β-gluco-, 2-deoxy-β-gluco-
- Nagai, Hideyuki,Sasaki, Kaname,Matsumura, Shuichi,Toshima, Kazunobu
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p. 337 - 353
(2007/10/03)
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- Glycosylation with trichloroacetimidates in ionic liquids: Influence of the reaction medium on the stereochemical outcome
-
The glycosylation with trichloroacetimidates derived from different glycopyranoses bearing a nonparticipating group at C-2 was explored in different ionic liquids as solvents. The stereoselectivity of the reaction was significantly affected by the reactio
- Rencurosi, Anna,Lay, Luigi,Russo, Giovanni,Caneva, Enrico,Poletti, Laura
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p. 7765 - 7768
(2007/10/03)
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- A novel glycosidation of glycosyl fluoride using a designed ionic liquid and its effect on the stereoselectivity
-
The glycosidations of glucopyranosyl fluoride and alcohols using an ionic liquid containing a protic acid effectively proceeded under mild conditions to afford the corresponding glycosides in good to high yields. The stereoselectivity of the glycosidation
- Sasaki, Kaname,Matsumura, Shuichi,Toshima, Kazunobu
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p. 7043 - 7047
(2007/10/03)
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- Trichloroacetimidates as Glycosyl Donors in Recyclable Ionic Liquids
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The trichloroacetimidates of different glycopyranoses were glycosylated in ionic liquids with different acceptors, affording the corresponding glycopyranosides in fair to excellent yields and allowing to recycle the solvent without additional Lewis acid.
- Poletti, Laura,Rencurosi, Anna,Lay, Luigi,Russo, Giovanni
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p. 2297 - 2300
(2007/10/03)
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- Environmentally benign and stereoselective formation of β-O-glycosidic linkages using benzyl-protected glucopyranosyl phosphite and montmorillonite K-10
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An environmentally benign and highly stereoselective β-glucopyranosylation without neighboring group participation has been developed employing benzyl-protected glucopyranosyl diethyl phosphite as a glycosyl donor and montmorillonite K-10 as an activator.
- Nagai, Hideyuki,Matsumura, Shuichi,Toshima, Kazunobu
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p. 847 - 850
(2007/10/03)
-
- A new, efficient glycosylation method for oligosaccharide synthesis under neutral conditions: Preparation and use of new DISAL donors
-
Efficient, stereoselective glycosylation methods are required for the synthesis of complex oligosaccharides as tools in glycobiology. All glycosylation methods, which have found wide acceptance, rely on Lewis acid activation of glycosyl donors prior to glycosylation. Here, we present a new and efficient method for glycosylation under neutral or mildly basic conditions. Glycosides of methyl 2-hydroxy-3,5-dinitrobenzoate (DISAL) and its para regioisomer, methyl 4-hydroxy-3,5-dinitrobenzoate, were prepared by nucleophilic aromatic substitution. In a first demonstration of their potential as glycosyl donors, stereospecific glycosylation of methanol was achieved. In the glycosylation of more hindered alcohols, the β-donor proved more reactive, and α-glucosides were predominantly formed. Glycosylation of protected monosaccharides, with free 6-0H or 3-OH, proceeded smoothly in 1-methyl-2-pyrrolidinone (NMP) at 40-60 °C in the absence of Lewis acids and bases in good to excellent yields. Glycosylation of 3-OH gave the α-linked disaccharide only.
- Petersen,Jensen
-
p. 6268 - 6275
(2007/10/03)
-
- Stereoselective O-glycosylation reactions using glycosyl donors with diphenylphosphinate and propane-1,3-diyl phosphate leaving groups
-
Glycosyl donors having a diphenylphosphinate and a propane-1,3-diyl phosphate leaving group were easily prepared by the addition of the anomeric hydroxyl group of 2,3,4,6-tetra-O-benzyl-α,β-D-glucopyranose to diphenylphosphinic and propane-1,3- diyldioxyphosphoryl chlorides. These glycosyl donors were selectively glycosylated with a number of primary and secondary oxygen nucleophiles in the presence of trimethylsilyl triflate (TMSOTf). The use of 1,3-diyl phosphate resulted in the stereoselective formation of β-O-linked glycosides.
- Vankayalapati, Hariprasad,Singh, Gurdial,Tranoy, Isabelle
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p. 1373 - 1381
(2007/10/03)
-
- Dehydrative glycosylation with activated diphenyl sulfonium reagents. Scope, mode of C(1)-hemiacetal activation, and detection of reactive glycosyl intermediates
-
The development of a method for direct dehydrative glycosylations with 1-hydroxyglycosyl donors employing the reagent combination of triflic anhydride and diphenyl sulfoxide is described. The one-pot coupling method is a facile process which is applicable
- Garcia,Gin
-
p. 4269 - 4279
(2007/10/03)
-
- First synthesis of anomeric sulfimides - Efficient glycosyl donors
-
Sugar-derived anomeric sulfimides were prepared in high yields from the corresponding thioglycosides and their ability to act as glycosyl donors was investigated.
- Cassel, Stephanie,Plessis, Isabelle,Wessel, Hans Peter,Rollin, Patrick
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p. 8097 - 8100
(2007/10/03)
-
- Stereoselective O-glycosylation reactions employing diphenylphosphinate and propane-1,3-diyl phosphate as anomeric leaving groups
-
Glycosidation of tetra-O-benzyl-D-glucose using diphenylphosphinate as the leaving group afforded β-O-linked glycosides as the major products, whilst the use of propane-1,3-diyl phosphate as the leaving group resulted in the exclusive formation of β-O-lin
- Hariprasad, Vankayalapati,Singh, Gurdial,Tranoy, Isabelle
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p. 2129 - 2130
(2007/10/03)
-
- O-Glycoside Synthesis under Neutral Conditions in Concentrated Solutions of LiClO4 in Organic Solvents Employing Benzyl-Protected Glycosyl Donors
-
The benzyl-protectd glucosyl trichloroacetimidates, phosphates, and halides 1 are activated under neutral conditions and without the addition of any further promoter in 1 M solutions of LiCl4 in ether, CH2Cl2, CHCl3, or CH3CN and react under these conditi
- Boehm, Gerd,Waldmann, Herbert
-
p. 613 - 620
(2007/10/03)
-
- THIOGLYCOSIDES AS POTENTIAL GLYCOSYL DONORS IN ELECTROCHEMICAL GLYCOSYLATION REACTIONS. PART 1: THEIR PREPARATION AND REACTIVITY TOWARD SIMPLE ALCOHOLS
-
Costant potential electrolysis of several glycosyl donors such as substituted phenyl 2,3,4,6-tetra-O-acetyl, benzoyl or benzyl-1-thio-β-D-gluco or galactopyranosides in dry acetonitrile in the presence of various primary, secondary or tertiary alcohols performed in an undivided cell, gave preferentially β-linked saccharides in moderate to good yields according to the nature of the protective groups on the sugar moiety. 2-Deoxy-2-phthalimido-1-thio-β-D-gluco derivatives gave the β-glucosides selectively in excellent yields.It was found, as expected, that substitution of the phenyl group with methoxy or methyl radicals facilitates the electrochemical glycosylation reaction by lowering the oxidation potentials of the corresponding thioglycosides.
- Balovoine, Gilbert,Berteina, Sabine,Gref, Aurore,Fischer, Jean-Claude,Lubineau, Andre
-
p. 1217 - 1236
(2007/10/03)
-
- Anomeric O-Alkylation, 9. Disaccharide Synthesis via Anomeric O-Alkylation
-
Base-promoted reaction of tetra-O-benzyl-glucose 1a with secondary alkyl trifluoromethanesulfonates 2 and 3 in toluene provides in the presence of 15-crown-5 preferentially β-glycosides 2aβ and 3aβ, respectively, in high yields.For reactions carried out a
- Tsvetkov, Yury E.,Klotz, Wolfgang,Schmidt, Richard R.
-
p. 371 - 376
(2007/10/02)
-
- Glycosylidene Carbenes. Part 6. Synthesis of Alkyl and Fluoroalkyl Glycosides
-
The synthesis of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolitic conditions are described.Yields and diastereoselectivities depend upon the pKHA values of the alcohols, the solvent, and the reaction temperature.The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH2Cl2 at room temperature leads to the glycosides 2-5 in yields between 60 and 34percent (Scheme I and Table 1) At -70 to -60 deg, yields are markedly higher.In CH2Cl2, diastereoselectivities are very low.In THF, at -70 to -60 deg, however, glycosidation of i-PrOH leads to α-D-/β-D-4 in a ratio of 8:92.More strongly acidic alcohols, such as CF3CH2OH, (CF3)2CHOH, and (CF3)2C(Me)OH, and the highly fluorinated long-chain alcohols CF3(CF2)5(CH2)2OH (11) and CHF2(CF2)9CH2OH (13) react (CH2Cl2, r.t.) in yields between 73 and 85percent and lead mainly to the β-D-glucosides β-D-6 to β-D-8, β-D-12, and β-D-14 (d.e. 14-68percent).Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimethoxyethane, or THF are used, as examined for the glycosidation of (CF3)2C(Me)OH, yielding (1,2-dimethoxyethane, 25 deg) 80percent of α-D-/β-D-8 in a ratio of 2:98 (d.e. 96percent; Table 4).In EtCN, (CF3)2C(Me)OH yields up to 55percent of the imidate 10.Glycosidation of di-O-isopropylidene-glucose 15 leads to 16 (CH2Cl2, r.t; 65percent, α-D/β-D=33:67).That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10, derived from the attack of (CF3)2MeCO(1-) on an intermediate nitrilium ion (Scheme 4), and, for weakly acidic alcohols, by the formation of α-D-9 and β-D-9, derived by attack of i-PrO(1-) on intermediate tetrahydrofuranylium ions.A working hypothesis is presented (Scheme 3).The diastereoselectivities are rationalized on the basis of a protonation in the ? plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO-C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO(1-) in the ? plane of the (solvated) oxonium ion.
- Briner, Karin,Vasella, Andrea
-
p. 621 - 637
(2007/10/02)
-
- Stereoselective synthesis of α-linked saccharides by use of per O-benzylated 2-pyridyl 1-thio hexopyranosides as glycosyl donors and methyl iodide as an activator
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A new, practical, stereoselective glycosidation methodology is described where per O-benzylated 2-pyridyl 1-thio-α/β-hexopyranosyl donors of D-gluco-(1), D-galacto- (2), D-manno- (3) and L-rhamno- (4) configurations have been efficiently coupled with dive
- Mereyala,Reddy
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p. 6435 - 6448
(2007/10/02)
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- Glycosylidene Carbenes Part 5 Synthesis of Glycono-1,5-lactone Tosylhydrazones as Precursors of Glycosylidene Carbenes
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The benzyl- and the acyl-protected glyconolactone tosylhydrazones 6, 9, 12, 16, and 19 (Scheme 1) were prepared in good yields by treating the hemiacetals 4, 7, 10, 14, and 17 with N-tosylhydrazine, to give the N-glycosylhydrazines 5, 8, 11, 15, and 18, a
- Mangholz, Sissi E.,Vasella, Andrea
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p. 2100 - 2111
(2007/10/02)
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- 2-(Trimethylsilyl)ethyl Glycosides. Transformation into Glycopyranosyl Chlorides
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2-(Trimethylsilyl)ethyl (TMSET) glycosides were transformed in high yields into the corresponding 1-chloro sugars by treatment with 1,1-dichloromethyl methyl ether/zinc chloride.With acetyl, benzoyl, and benzyl protection of the 2-postion, the α-glycopyranosyl chloride was the major product, whereas with the 2-phthalimido sugar 13, the β-chloride 21 was obtained.The fully benzylated TMSET glucopyranoside 1 gave the α-chloro sugar 22 carrying a 6-O-formyl group whereas the partially benzylated sugars 16 and 17 gave the chloro sugars with all protecting groups intact.
- Jansson, Karl,Noori, Ghazi,Magnusson, Goeran
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p. 3181 - 3185
(2007/10/02)
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