- Ir(I)-Catalyzed C?H Glycosylation for Synthesis of 2-Indolyl-C-Deoxyglycosides
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The construction of 2-deoxy-C-glycosides has gradually become a hotspot of carbohydrate chemistry in recent years. In this work, we present an efficient, regioselective, stereoselective and widely applicable strategy for the synthesis of 2-indolyl-C-deoxyglycosides via Ir(I)-catalyzed, pyridine-group-directed C?H functionalization. This method exhibits high tolerance for the functional groups of indoles and the protecting groups of carbohydrates. Moreover, this protocol has good stereoselectivity and mainly produces β-configuration products. Gram-scale synthesis and several practical transformations were conducted for further applications. Meantime, we also explored the mechanism of this method and proposed a catalytic cycle. (Figure presented.).
- Yu, Changyue,Liu, Yichu,Xie, Xiong,Hu, Shulei,Zhang, Shurui,Zeng, Mingjie,Zhang, Dan,Wang, Jiang,Liu, Hong
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supporting information
p. 4926 - 4931
(2021/09/09)
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- Rhodium-Catalyzed Denitrogenative Transannulation of N-Sulfonyl-1,2,3-triazoles with Glycals Giving Pyrroline-Fused N-Glycosides
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Described here is a selective synthesis of 2,3-dihydropyrrole-fused N-glycosides through rhodium-catalyzed denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles with glycals. A series of pyrroline-fused N-glycosides are afforded in moderate to exc
- Bi, Jingjing,Tan, Qiang,Wu, Hao,Liu, Qingfeng,Zhang, Guisheng
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supporting information
p. 6357 - 6361
(2021/08/23)
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- Iron-Catalyzed Radical Cleavage/C?C Bond Formation of Acetal-Derived Alkylsilyl Peroxides
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A novel radical-based approach for the iron-catalyzed selective cleavage of acetal-derived alkylsilyl peroxides, followed by the formation of a carbon–carbon bond is reported. The reaction proceeds under mild reaction conditions and exhibits a broad substrate scope with respect to the acetal moiety and the carbon electrophile. Mechanistic studies suggest that the present reaction proceeds through a free-radical process involving carbon radicals generated by the homolytic cleavage of a carbon–carbon bond within the acetal moiety. A synthetic application of this method to sugar-derived alkylsilyl peroxides is also described.
- Shiozaki, Yoko,Sakurai, Shunya,Sakamoto, Ryu,Matsumoto, Akira,Maruoka, Keiji
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supporting information
p. 573 - 576
(2020/02/20)
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- Method for preparing 3,4,6-tri-O-substituent-D-glucal
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The invention discloses a method for preparing 3,4,6-tri-O-substituent-D-glucal. The method comprises the following steps: (1) preparation of D-glucal: subjecting 3,4,6-tri-O-acetyl-D-glucal, which serves as a starting raw material, to a reaction under al
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Paragraph 0021; 0022; 0023
(2019/02/04)
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- Carbonylative Negishi-Type Coupling of 2-Iodoglycals with Alkyl and Aryl Halides
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C-Glycosides are valuable organic compounds in the field of medicinal chemistry due to their ubiquity inside living systems and pronounced biological activity. Herein, we describe an approach to alkyl-ketones bearing glycal units via the Pd-catalyzed carb
- Esteves, Henrique A.,Darbem, Mariana P.,Pimenta, Daniel C.,Stefani, Hélio A.
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supporting information
p. 7384 - 7388
(2019/11/28)
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- Palladium catalyzed stereocontrolled synthesis of C-aryl glycosides using glycals and arenediazonium salts at room temperature
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A stereocontrolled synthesis of aryl-C-glycosides was achieved using glycals and aryldiazonium salts in the presence of palladium acetate. A wide range of glycals including d-glucal, d-galactal, l-rhamnal, d-xylal and d-ribal underwent C-arylation at the anomeric carbon in the presence of different aryldiazonium tetrafluoroborates and gave synthetically useful 2,3-deoxy-3-keto-α-aryl-C-glycosides in good to excellent yields. Broad substrate scope, simple operation and room temperature reactions make this protocol very attractive in organic synthesis.
- Singh, Adesh Kumar,Kandasamy, Jeyakumar
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supporting information
p. 5107 - 5112
(2018/07/29)
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- Effects of lipophilicity, protecting group and stereochemistry on the antimalarial activity of carbohydrate-derived thiochromans
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A series of novel carbohydrate-derived thiochromans has been successfully synthesized in order to investigate the influence of alkyl substituents on the aromatic ring of the thiophenol moiety in addition to the effect of protecting groups and stereochemistry on the sugar component of the target molecules. Results from the evaluation of the thiochromans for their antimalarial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum suggest that the presence of short chain alkyl substituents, a benzyl ether protecting group and equatorial orientation of the C-4 substituent on the sugar moiety are crucial structural features that impart high antimalarial activity.
- Madumo, Gilbert K.,Moshapo, Paseka T.,Kinfe, Henok H.
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p. 817 - 833
(2018/01/10)
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- Direct C-H Trifluoromethylation of Glycals by Photoredox Catalysis
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A mild, efficient, and practical transformation for the direct C-H trifluoromethylation of glycals under visible light has been reported for the first time. This reaction employed fac-Ir3+(ppy)3 as the photocatalyst, Umemoto's reagent as the CF3 source, and a household blue LED or sunlight as the light source. Glycals bearing both electron-withdrawing and -donating protective groups performed this reaction smoothly. This visible light-mediated trifluoromethylation reaction was highlighted by the trifluoromethylation of the biologically important Neu2en moiety.
- Wang, Bang,Xiong, De-Cai,Ye, Xin-Shan
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supporting information
p. 5698 - 5701
(2015/12/01)
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- α-Selective organocatalytic synthesis of 2-deoxygalactosides
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Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety (see scheme). The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. Copyright
- Balmond, Edward I.,Coe, Diane M.,Galan, M. Carmen,McGarrigle, Eoghan M.
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supporting information
p. 9152 - 9155
(2012/10/29)
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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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- N-heterocyclic carbene catalyzed C-glycosylation: A concise approach from stetter reaction
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Described herein is the first example of an organocatalytic approach for acylanion addition to the anomeric carbon of 2-nitroglucal using an N-heterocyclic carbene catalyst. Control over the reaction conditions gives β-selective and nitro-eliminated C-glycosides, providing opportunities to produce new classes of C-glycoside.
- Vedachalam, Seenuvasan,Tan, Shi Min,Teo, Hui Ping,Cai, Shuting,Liu, Xue-Wei
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supporting information; experimental part
p. 174 - 177
(2012/02/16)
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- En route to sugar-alkaloid conjugates
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After stereoselective addition of N-iodosuccinimide to glycals subsequent dehalogenation results in formation of N-glycopyranosyl succinimides. By UV irradiation both azepindiones and preferentially [5.3.1.02,6] tricyclic oxalactams could be ob
- Sowa, Carsten-Endres,Thiem, Joachim
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experimental part
p. 1546 - 1550
(2011/09/12)
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- Erosion of stereochemical control with increasing nucleophilicity: O-glycosylation at the diffusion limit
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(Chemical Equation Presented) Nucleophilic substitution reactions of 2-deoxyglycosyl donors indicated that the reactivity of the oxygen nucleophile has a significant impact on stereoselectivity. Employing ethanol as the nucleophile resulted in a 1:1 (α:β) ratio of diastereomers under SN1-like reaction conditions. Stereoselective formation of the 2-deoxy-α-O-glycoside was only observed when weaker nucleophiles, such as trifluoroethanol, were employed. The lack of stereoselectivity observed in reactions of common oxygen nucleophiles can be attributed to reaction rates of the stereochemistry-determining step that approach the diffusion limit. In this scenario, both faces of the prochiral oxocarbenium ion are subject to nucleophilic addition to afford a statistical mixture of diastereomeric products. Control experiments confirmed that all nucleophilic substitution reactions were performed under kinetic control.
- Beaver, Matthew G.,Woerpel
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supporting information; experimental part
p. 1107 - 1118
(2010/04/06)
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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
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supporting information; experimental part
p. 8724 - 8728
(2011/01/06)
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- Synthesis of glycal-based chiral benzimidazoles by VO(acac) 2-CeCl3 combo catalyst and their self-aggregated nanostructured materials
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(Figure Presented) VO(acac)2-CeCl3 combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2′-C-3′,4′,6′-tri-O-benzyl/methyl-glycal)-1H- benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d] imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported. 2009 American Chemical Society.
- Maiti, Dilip K.,Halder, Samiran,Pandit, Palash,Chatterjee, Nirbhik,De Joarder, Dripta,Pramanik, Nabyendu,Saima, Yasmin,Patra, Amarendra,Maiti, Prabir K.
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supporting information; experimental part
p. 8086 - 8097
(2010/02/28)
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- Correlations between nucleophilicities and selectivities in the substitutions of tetrahydropyran acetals
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(Chemical Equation Presented) Selectivities that deviate from S N1 stereoelectronic models in the nucleophilic substitutions of tetrahydropyran acetals were investigated. When weak nucleophiles were employed, stereoselectivities conformed to kn
- Krumper, Jennifer R.,Salamant, Walter A.,Woerpel
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supporting information; experimental part
p. 8039 - 8050
(2010/02/28)
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- Synthesis of pyranoid and furanoid glycals from glycosyl sulfoxides by treatment with organolithium reagents
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Glycosyl sulfoxides can be conveniently transformed into pyranoid or furanoid glycals by treatment with organolithium reagents. The more likely reaction pathway involves a sulfoxide/metal exchange reaction to generate a glycosyllithium derivative that und
- Gomez, Ana M.,Casillas, Marta,Barrio, Aitor,Gawel, Anna,Lopez, J. Cristobal
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experimental part
p. 3933 - 3942
(2009/04/08)
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- Synthesis and evaluation of pyrazolo[3,4-b]pyridines and its structural analogues as TNF-α and IL-6 inhibitors
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In the present article, we have synthesized three different series of pyrazolo[3,4-b]pyridines and their structural analogues using novel synthetic strategy involving one-pot condensation of 5,6-dihydro-4H-pyran-3-carbaldehyde/2-formyl-3,4,6-tri-O-methyl-d-glucal /chromone-3-carbaldehyde with heteroaromatic amines. All synthesized compounds were evaluated for their anti-inflammatory activity against TNF-α and IL-6. Out of 28 compounds screened, 40, 51, 52 and 56 exhibited promising activity against IL-6 with 60-65% inhibition at 10 μM concentration. Amongst these, 51, 52 and 56 showed potent IL-6 inhibitory activity with IC50's of 0.2, 0.3 and 0.16 μM, respectively. Compound 56 was not cytotoxic in CCK-8 cells up to the concentration of >100 μM.
- Bharate, Sandip B.,Mahajan, Tushar R.,Gole, Yogesh R.,Nambiar, Mahesh,Matan,Kulkarni-Almeida, Asha,Balachandran, Sarala,Junjappa,Balakrishnan, Arun,Vishwakarma, Ram A.
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p. 7167 - 7176
(2008/12/22)
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- Tandem epoxidation-alcoholysis or epoxidation-hydrolysis of glycals catalyzed by titanium(IV) isopropoxide or Venturello's phosphotungstate complex
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Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr)4] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H2O 2]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr)4 was only effective in methanol as solvent, but gave methyl glycosides in high yields and high selectivities. The Venturello complex proved to be a very versatile and efficient catalyst. Apart from epoxidation-alcoholysis in alcoholic solvents it also showed activity in biphasic conditions to allow for glycosylation of long-chain alcohols and was very effective in the stereoselective dihydroxylation of benzylated glucal.
- Levecque, Pieter,Gammon, David W.,Kinfe, Henok Hadgu,Jacobs, Pierre,De Vos, Dirk,Sels, Bert
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supporting information; experimental part
p. 1557 - 1568
(2009/07/10)
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- Remarkable oxidation stability of glycals: Excellent substrates for cerium(IV)-mediated radical reactions
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The remarkable stability of glycals under oxidative conditions becomes apparent by their redox data in solution, computed HOMO energies, and behavior on the addition of electrophilic radicals generated in the presence of cerium(IV) ammonium nitrate. Oxida
- Linker, Torsten,Schanzenbach, Dirk,Elamparuthi, Elangovan,Sommermann, Thomas,Fudickar, Werner,Gyollai, Viktor,Somsak, Laszlo,Demuth, Wolfgang,Schmittel, Michael
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supporting information; experimental part
p. 16003 - 16010
(2009/05/15)
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- Direct one-pot conversion of acylated carbohydrates into their alkylated derivatives under heterogeneous reaction conditions using solid NaOH and a phase transfer catalyst
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A convenient one-pot protocol for the direct conversion of acyl-protected carbohydrates into their alkylated counterparts has been developed by using alkyl halides in the presence of solid sodium hydroxide and a phase transfer catalyst. These economically
- Madhusudan, Soni Kamlesh,Agnihotri, Geetanjali,Negi, Devendra S.,Misra, Anup Kumar
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p. 1373 - 1377
(2007/10/03)
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- 5-CYCLO INDOLE COMPOUNDS AS 5-HT1D RECEPTOR LIGANDS
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Described herein are compounds selective for a 5-HT1D-like receptor, which have general formula (I), wherein A is selected from a six-membered, non-aromatic, optionally substituted carbocycle and a six-membered, non-aromatic, optionally substituted heterocycle having one or two heteroatoms selected from O, S, SO, SO2 and NR; R is selected from H and OH; n is 0 or 1 as permitted by chemical structure; R is selected from CRRCH2NRR or a group of formula (II), (III) or (IV); R is selected from H and benzoyl; R is selected from H, loweralkyl, benzyl, loweralkylcarbonyl, loweralkylaminocarbonyl; loweralkylaminothiocarbonyl, loweralkanoyl, loweralkylaminoimide and loweralkoxy-substituted loweralkylene; R and R are independently selected from H, loweralkoxy and hydroxy; R and R are independently selected from H and loweralkyl or R and R form an alkylene bridge which, together with the nitrogen atom to which they are attached, creates an optionally substituted 3- to 6-membered ring; ----- denotes a single or double bond; and R, R and R are independently selected from H and loweralkyl. Also described is the use of these compounds as pharmaceuticals to treat indications where stimulation of a 5-HT1D-like receptor is implicated, such as migraine.
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Page/Page column 14
(2008/06/13)
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- Rapid preparation of variously protected glycals using titanium(III)
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Glycosyl chlorides and bromides can be rapidly converted to glycals in high yield by reaction with (Cp2Ti[III]Cl)2. This reagent tolerates a wide range of common carbohydrate protecting groups, including silyl ethers, acetals, and esters; the methodology provides a general route for the preparation of glycals substituted with both acid- and base-labile functionality. A reaction mechanism is proposed that is based on heteroatom abstraction to give an intermediate glycosyl radical. This radical reacts with a second equivalent of Ti(III) to yield a glycosyltitanium(IV) species. β-Heteroatom elimination from the glycosyltitanium(IV) complex gives the glycal.
- Spencer, Roxanne P.,Cavallaro, Cullen L.,Schwartz, Jeffrey
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p. 3987 - 3995
(2007/10/03)
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- THE ALKYLATION AND ACYLATION OF GLYCALS VIA AN INITIALIZING ELECTROCHEMICAL STEP
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The method of electrochemically induced formation of ether and ester derivatives of saturated mono- and disaccharides was applied to 1,2-unsaturated monosaccharides (D-glycals).The influence of the supporting electrolyte on the product distribution was investigated by variation of the cation.To provide data for comparison, alkylation was also carried out chemically in the presence of different bases, e.g.LiH and NaH.
- Fischer, Susanne,Hamann, Carl Heinz
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p. 327 - 340
(2007/10/02)
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- The Chemistry of Glucal Halohydrins: The Effect of the Halide on Epoxide Formation
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Chlorohydrins, bromohydrins, and iodohydrins, formed by hydroxyhalogenation of tri-O-methyl glucal, undergo base induced cyclization to give glucal epoxides.The mechanism of the cyclization reaction was probed using 1H NMR and deuterium incorporation studies.Cyclization and in situ trapping with Cs2CO3 in MeOD gave deuterated methyl 3,4,6-tri-O-methyl-α-D-mannoside and methyl 3,4,6-tri-O-methyl-β-D-glucoside, and an unsaturated aldehyde.These studies led to optimised stereoselectivity for the epoxide formation.Reaction of gluco bromohydrins with NaH or LiHMDS in THF at 5 deg C gave β-epoxide, and reaction of manno iodohydrins with KH and 18-crown-6 in toluene at -70 deg C gave α-epoxide.The epoxides were opened by reaction with sodium phenylthiolate to give phenyl 3,4,6-tri-O-methyl-1-thio-α-D-mannopyranoside (single isomer), and phenyl 3,4,6-tri-O-methyl-1-thio-β-D-glucopyranoside (>18:1), respectively.
- Marzabadi, Cecilia H.,Spilling, Christopher D.,Tyler, Lisa M.
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p. 6783 - 6796
(2007/10/02)
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- The facile conversion of pyranoid glycals into 2-deoxy-glycosidic orthoesters
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The formation of 2-deoxy-glycosidic orthoesters involving the palladium(II) catalysed reaction of pyranoid glycals with alcohols in the presence of sodium hydrogen carbonate is described.
- Holzapfel, Cedric W.,Engelbrecht, Gerhardus J.,Verdoorn, Gerhard H.
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p. 433 - 444
(2007/10/02)
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- 2-NITROGLYCALS - PREPARATION AND NUCLEOPHILIC ADDITION REACTIONS
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2-Nitroglycals were prepared by reaction of the corresponding glycals with nitronium tetrafluoroborate and base.The stereoselective Michael addition reactions of O-alkyl-2-nitroglucals with a number of nucleophiles are described.
- Holzapfel, C. W.,Marais, C. F.,Dyk, M. S. van
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- Regioselective Synthesis of Substituted 1-Thiohex-2-enopyranosides
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A variety of 1-thiohex-2-enopyranosides have been prepared from their corresponding 3-O-methyl- or 3-O-acetylglycals by using trimethylsilyl thiols catalyzed by BF3 etherate.This method is regioselective for thiolation at C-1 in contrast to the same react
- Dunkerton, Lois V.,Adair, Nancy K.,Euske, Jack M.,Brady, Kevin T.,Robinson Paul D.
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p. 845 - 850
(2007/10/02)
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- Synthesis of C-Glucosides by Reactions of Glucosyl Halides with Organocuprates.
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Lithium dimethylcuprate reacts with trans-2-chloro-6-methyltetrahydropyran (1) via nucleophilic substitution predominantly with inversion of configuration to afford cis-2,6-dimethyltetrahydropyran (2).Similarly, lithium dialkylcuprates displace protected α-glucosyl bromides (5) with inversion to afford the β-C-glucosides, β-1-alkyl-1,5-anhydroglucitols (6).In contrast, Grignard reagents gave mixtures of α- and β- glucosides 6 and 7, while organolithium reagents gave only elimination to 9.
- Bihovsky Ron,Selick Caryn,Giusti Irena
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p. 4026 - 4031
(2007/10/02)
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- CYCLOADDITION OF TRICHLOROACETYL ISOCYANATE TO GLYCALS
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Cycloaddition of trichloroacetyl isocyanate to 1,5-anhydro-2-deoxy-D-erythro- and -L-threo-pent-1-enitols, and 1,5-anhydro-2-deoxy-D- and -L-arabino-hex-1-enitols having benzyl, methyl, tert-butyldimethylsilyl, and trimethylsilyl substituents on hydroxyl groups proceeds satisfactorily, under normal pressure at room temperature, to give a mixture of and cycloadducts.The isocyanate enters the glycal molecule stereospecifically anti with respect to the C-3 substituent.Bicyclic adducts slowly rearrange to the respective α,β-unsaturated amides.N-Deprotection of the trichloroacetyl substituent in cycloadducts produces stable β-lactams.Further deprotection gives crystalline, water-soluble 2-carboxy-2-deoxypento- and -hexo-pyranosylaminolactams having a unique bicyclic sugar structure.
- Chmielewski, Marek,Kaluza, Zbigniew
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p. 143 - 152
(2007/10/02)
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- Preparation and reductive lithiation of 2-deoxy-D-glucopyranosyl phenylsulfones: A highly stereoselective route to C-glycosides
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2-Deoxy-D-glucopyranosyl phenylsulfones 3a-c have been synthesized in 75-83% yield from commercial tri-O-acetyl-D-glucal 1. Their reductive desulfonylation by lithium naphthalenide and reaction of the intermediate glycosyl-lithium 5 with aldehydes leads t
- Beau,Sinay
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p. 6185 - 6188
(2007/10/02)
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