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DIASTEREOSELECTIVE SYNTHESIS OF BRANCHED 2-DEOXY SUGARS VIA RADICAL C-C BOND FORMATION REACTIONS
From glycals 1 and 6, 2-deoxy sugars can be synthesized in 40-72percent yields.With 1,2-disubstituted alkenes 3 this radical C-C bond formation reaction leads with high stereoselectivity to the isomers 4 and 8.
Giese, Bernd,Groeninger, Kay
p. 2743 - 2746
(1984)
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2-nitroglycal and efficient synthesis method thereof
The invention discloses an efficient synthesis method of 2-nitroglycal, and belongs to the technical field of synthesis of sugar. The structure of the 2-nitroglycal is shown in the specification. Secondly, the invention also provides a preparation method of the 2-nitro saccharide alkene, and the preparation method provided by the invention can be used for efficiently preparing the 2-nitroglycal through one-step synthesis.
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Paragraph 0056-0058

(2021/08/06)

Me3SI-promoted chemoselective deacetylation: a general and mild protocol
A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
p. 19310 - 19315
(2021/06/03)

Ir(I)-Catalyzed C?H Glycosylation for Synthesis of 2-Indolyl-C-Deoxyglycosides
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
supporting information
p. 4926 - 4931
(2021/09/09)

Total Synthesis of Tri-, Hexa- and Heptasaccharidic Substructures of the O-Polysaccharide of Providencia rustigianii O34
A general and efficient strategy for synthesis of tri-, hexa- and heptasaccharidic substructures of the lipopolysaccharide of Providencia rustigianii O34 is described. For the heptasaccharide seven different building blocks were employed. Special features of the structures are an α-linked galactosamine and the two embedded α-fucose units, which are either branched at positions-3 and -4 or further linked at their 2-position. Convergent strategies focused on [4+3], [3+4], and [4+2+1] couplings. Whereas the [4+3] and [3+4] coupling strategies failed the [4+2+1] strategy was successful. As monosaccharidic building blocks trichloroacetimidates and phosphates were employed. Global deprotection of the fully protected structures was achieved by Birch reaction.
Ahadi, Somayeh,Awan, Shahid I.,Werz, Daniel B.
(2020/05/04)

A Potent Mimetic of the Siglec-8 Ligand 6’-Sulfo-Sialyl Lewisx
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved.
Conti, Gabriele,Cramer, Jonathan,Ernst, Beat,Girardi, Benedetta,Jiang, Xiaohua,Kokot, Maja,Kroezen, Blijke S.,Luisoni, Enrico,Müller, Jennifer,Rabbani, Said,Ricklin, Daniel,Schwardt, Oliver
supporting information
p. 1706 - 1719
(2020/09/02)

Method for stereoselectively synthesizing beta-2-deoxyglycoside bond
The invention discloses a method for stereoselectively synthesizing a beta-2-deoxyglycoside bond. The method comprises the following steps: performing glycosylation on 3,4-O-isopropylidene-6-O-tert-butyl diphenylmethyl silicone-D-galactosene serving as a donor, a saccharide receptor and a molecular sieve under the condition of the existence of an accelerant, wherein an isopropyl acetal protectivegroup is mounted on a 3-site hydroxyl and a 4-site hydroxyl of the 3,4-O-isopropylidene-6-O-tert-butyl diphenylmethyl silicone-D-galactosene and a TBDPS is mounted on the 6-site of the 3,4-O-isopropylidene-6-O-tert-butyl diphenylmethyl silicone-D-galactosene; through the synergistic effect of the protective groups, sugar ring conformation of the donor is controlled, and the stereoselective synthesis of a beta-configuration is realized. According to the method, the stereoselectivity of the glycosylation can be controlled effectively and stereoselectively; the method is wide in substrate application range and convenient to operate; raw materials are easy to obtain; side reactions of the glycosylation are few; a target product is high in yield and optical purity; a new design thought is provided for the research of the glycosylation.
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(2019/07/04)

Total Synthesis of the Congested, Bisphosphorylated Morganella morganii Zwitterionic Trisaccharide Repeating Unit
Zwitterionic polysaccharides (ZPSs) activate T-cell-dependent immune responses by major histocompatibility complex class II presentation. Herein, we report the first synthesis of a Morganella morganii ZPS repeating unit as an enabling tool in the synthesis of novel ZPS materials. The repeating unit incorporates a 1,2-cis-α-glycosidic bond; the problematic 1,2-trans-galactosidic bond, Gal-β-(1 → 3)-GalNAc; and phosphoglycerol and phosphocholine residues which have not been previously observed together as functional groups on the same oligosaccharide. The successful third-generation approach leverages a first in class glycosylation of a phosphoglycerol-functionalized acceptor. To install the phosphocholine unit, a highly effective phosphocholine donor was synthesized.
Keith, D. Jamin,Townsend, Steven D.
supporting information
p. 12939 - 12945
(2019/08/22)

Stereospecific C-Glycosylation by Mizoroki–Heck Reaction: A Powerful and Easy-to-Set-Up Synthetic Tool to Access α- and β-Aryl-C-Glycosides
A stereospecific Mizoroki–Heck cross-coupling of differently substituted glycals with haloarenes resulting in the exclusive formation of either α- or β-aryl-C-glycosides depending solely on the configuration at C3 was achieved. The reaction was easy to set up because no specific precautions were required concerning moisture or oxygen, and it proceeded by a chirality transfer from C3 to C1. After optimization of cross-coupling conditions, various prepared glycals (7 examples) and arenes (10 examples) were tested, leading stereospecifically to the corresponding aryl-C-glycosides with a carbonyl group at C3, thus opening up new horizons for the total synthesis of glycosylated natural products.
Mabit, Thibaud,Siard, Aymeric,Legros, Frédéric,Guillarme, Stéphane,Martel, Arnaud,Lebreton, Jacques,Carreaux, Fran?ois,Dujardin, Gilles,Collet, Sylvain
supporting information
p. 14069 - 14074
(2018/09/14)

Synthesis of Altrose Poly-amido-saccharides with β-N-(1→2)- d -amide Linkages: A Right-Handed Helical Conformation Engineered in at the Monomer Level
The design and synthesis of amide-linked saccharide oligomers and polymers, which are predisposed to fold into specific ordered secondary structures, is of significant interest. Herein, right-handed helical poly amido-saccharides (PASs) with β-N-(1→2)-d-amide linkages are synthesized by the anionic ring-opening polymerization of an altrose β-lactam monomer (alt-lactam). The right-handed helical conformation is engineered into the polymers by preinstalling the β configuration of the lactam ring in the monomer via the stereospecific [2+2] cycloaddition of trichloroacetyl isocyanate with a d-glycal possessing a 3-benzyloxy group oriented to the α-face of the pyranose. The tert-butylacetyl chloride initiated polymerization of the alt-lactam proceeds smoothly to afford stereoregular polymers with narrow dispersities. Birch reduction of the benzylated polymers gives water-soluble altrose PASs (alt-PASs) in high yields without degradation of the polymer backbone. Circular dichroism analysis shows the alt-PASs adopt a right-handed helical conformation in aqueous solutions. This secondary conformation is stable over a wide range of different conditions, such as pH (2.0 to 12.0), temperature (5 to 75 °C), ionic salts (2.0 M LiCl, NaCl, and KCl), as well as in the presence of protein denaturants (4.0 M urea and guanidinium chloride). Cytotoxicity studies reveal that the alt-PASs are nontoxic to HEK, HeLa, and NIH3T3 cells. The results showcase the ability to direct solution conformation of polymers through monomer design. This approach is especially well-suited and straightforward for PASs as the helical conformations formed result from constraints imposed by the relatively rigid and sterically bulky repeating units.
Xiao, Ruiqing,Dane, Eric L.,Zeng, Jialiu,McKnight, Christopher J.,Grinstaff, Mark W.
p. 14217 - 14223
(2017/10/17)

Efficient and green approach for the complete deprotection of O-acetylated biomolecules
A simple, efficient and mild strategy for the complete O-deacetylation of different per-acetylated biomolecules in aqueous media has been described. Different lipases were tested but only the commercial Amano lipase A from Aspergillus Niger catalyzed the complete deprotection of peracetylated α-glucose to glucose in excellent yield. The experimental conditions were tested, in particular the pH effect. The reaction was performed at different pHs considering the only enzymatic process was evaluated at pH 5 and the combination of enzymatic and chemical migration process was evaluated at higher pHs. Finally pH 7 and 25 °C were selected as best conditions. Thus this lipase fully hydrolyzed different peracetylated α-glycopyranosides (glucose, mannose, glucal, galactal) with >99% yields, whereas very good deprotecting yields (75-80%) were achieved for different acetylated β-glycopyranosides (galactose, ribofuranose) under these mild conditions. This strategy was successfully extended to the fully O-selective deprotection of acetylated nucleosides where >99% yield was rapidly obtained. No selectivity was observed for the N-deacetylation in amino acids and peptides.
Dunne, Anthony,Palomo, Jose M.
p. 88974 - 88978
(2016/10/03)

Direct C-H Trifluoromethylation of Glycals by Photoredox Catalysis
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
p. 5698 - 5701
(2015/12/01)

Selective S-deacetylation inspired by native chemical ligation: practical syntheses of glycosyl thiols and drug mercapto-analogues
Glycosyl thiols are useful building blocks for the construction of compounds of biological and synthetic importance. Herein, we report a practical synthetic approach toward the efficient synthesis of glycosyl thiols via chemo- and regioselective S-deacetylation inspired by native chemical ligation. This strategy allows the large scale synthesis of glycosyl thiols by simple purification steps without column chromatography. In addition, deacetylation reagents (DTT) could also be recovered and regenerated by a simple process. Thiol containing taxol and artemisinin analogues were successfully prepared based on this methodology. Finally, auranofin, a glucose-based oral drug used to treat rheumatoid arthritis, was synthesized in concise steps and overall high yields.
Shu, Penghua,Zeng, Jing,Tao, Jinyi,Zhao, Yueqi,Yao, Guangmin,Wan, Qian
supporting information
p. 2545 - 2551
(2015/04/22)

Divergent synthesis of 2-C-branched pyranosides and oxepines from 1,2-gem-dibromocyclopropyl carbohydrates
The ring opening of 1,2-(gem-dibromo)cyclopropyl carbohydrates by two different modes leads to either 2-C-(bromomethylene)pyranosides (using base) or 2-bromooxepines (using silver salts), as shown previously by us for a D-glucal-derived cyclopropane. The base-promoted ring opening is extended to encompass additional alcohol, thiol and amine nucleophiles, and diastereoisomeric cyclopropane precursors. Cross-coupling of the 2-C-(bromomethylene)pyranosides leads to extended 2-C-branched pyranosides. Silver-promoted ring expansion of the cyclopropyl carbohydrates in the presence of various alcohols is described. Cross-coupling of the resulting benzyl 2-bromooxepines affords 2-C-substituted oxepines.
Moore, Peter W.,Schuster, Julia K.,Hewitt, Russell J.,Stone, M. Rhia L.,Teesdale-Spittle, Paul H.,Harvey, Joanne E.
supporting information
p. 7032 - 7043
(2015/02/19)

Oxidative heck reaction of glycals and aryl hydrazines: A palladium-catalyzed C-glycosylation
An efficient Heck-type C-glycosylation of glycals via the C-N bond cleavage of aryl hydrazines has been developed. The flexibility of the reaction was tested by the substrate scope, consisting of glycals from different carbohydrate origins as well as aryl hydrazines with various substituents. Pure α-C-glycosides were obtained when (3R)-glycals were employed, whereas α,β mixtures were observed with (3S)-glycals.
Bai, Yaguang,Kim, Le Mai Hoang,Liao, Hongze,Liu, Xue-Wei
p. 8821 - 8825
(2013/09/24)

N-heterocyclic carbene catalyzed C-glycosylation: A concise approach from stetter reaction
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
p. 174 - 177
(2012/02/16)

Glycomimetic ligands for the human asialoglycoprotein receptor
The asialoglycoprotein receptor (ASGPR) is a high-capacity galactose-binding receptor expressed on hepatocytes that binds its native substrates with low affinity. More potent ligands are of interest for hepatic delivery of therapeutic agents. We report several classes of galactosyl analogues with varied substitution at the anomeric, C2-, C5-, and C6-positions. Significant increases in binding affinity were noted for several trifluoromethylacetamide derivatives without covalent attachment to the protein. A variety of new ligands were obtained with affinity for ASGPR as good as or better than that of the parent N-acetylgalactosamine, showing that modification on either side of the key C3,C4-diol moiety is well tolerated, consistent with previous models of a shallow binding pocket. The galactosyl pyranose motif therefore offers many opportunities for the attachment of other functional units or payloads while retaining low-micromolar or better affinity for the ASGPR.
Mamidyala, Sreeman K.,Dutta, Sanjay,Chrunyk, Boris A.,Preville, Cathy,Wang, Hong,Withka, Jane M.,McColl, Alexander,Subashi, Timothy A.,Hawrylik, Steven J.,Griffor, Matthew C.,Kim, Sung,Pfefferkorn, Jeffrey A.,Price, David A.,Menhaji-Klotz, Elnaz,Mascitti, Vincent,Finn
supporting information; experimental part
p. 1978 - 1981
(2012/03/11)

Fluorine-directed β-galactosylation: Chemical glycosylation development by molecular editing
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
supporting information; experimental part
p. 8208 - 8215
(2012/08/27)

Stereoelectronic factors in the stereoselective epoxidation of glycals and 4-deoxypentenosides
Glycals and 4-deoxypentenosides (4-DPs), unsaturated pyranosides with similar structures and reactivity profiles, can exhibit a high degree of stereoselectivity upon epoxidation with dimethyldioxirane (DMDO). In most cases, the glycals and their corresponding 4-DP isosteres share the same facioselectivity, implying that the pyran substituents are largely responsible for the stereodirecting effect. Fully substituted dihydropyrans are subject to a "majority rule", in which the epoxidation is directed toward the face opposite to two of the three groups. Removing one of the substituents has a variable effect on the epoxidation outcome, depending on its position and also on the relative stereochemistry of the remaining two groups. Overall, we observe that the greatest loss in facioselectivity for glycals and 4-DPs is caused by removal of the C3 oxygen, followed by the C5/anomeric substituent, and least of all by the C4/C2 oxygen. DFT calculations based on polarized-π frontier molecular orbital (PPFMO) theory support a stereoelectronic role for the oxygen substituents in 4-DP facioselectivity, but less clearly so in the case of glycals. We conclude that the anomeric oxygen in 4-DPs contributes toward a stereoelectronic bias in facioselectivity whereas the C5 alkoxymethyl in glycals imparts a steric bias, which at times can compete with the stereodirecting effects from the other oxygen substituents.
Alberch, Laura,Cheng, Gang,Seo, Seung-Kee,Li, Xuehua,Boulineau, Fabien P.,Wei, Alexander
scheme or table
p. 2532 - 2547
(2011/06/19)

Combining glycomimetic and multivalent strategies toward designing potent bacterial lectin inhibitors
As part of ongoing activities toward the design of potent and selective ligands against galactoside-binding proteins from animal, bacterial, and plant lectins, a systematic investigation involving the synthesis and binding evaluations of a series of original β-C-galactopyranoside mimetics is described. The multivalent presentation of partly optimized candidates on various dendritic scaffolds through CuI-catalyzed azide-alkyne cycloaddition (CuAAc) has also been achieved. Biophysical investigations based on isothermal titration calorimetry (ITC) have indicated a dissociation constant in the low micromolar range for the best optimized monovalent conjugate (K d=37 μM). The results thus confirmed that stable C-galactosides could represent efficient synthetic glycomimetics of natural α-linked oligosaccharidic inhibitors of PA-IL lectin (Lec A) from the pathogenic Pseudomonas aeruginosa. Striking enhancements in the avidity of the glycoconjugates were also observed for tri-, hexa-, and nonavalent derivatives, among which the most potent exhibited dissociation constants below 500 nM, corresponding to a 400-fold increase in affinity compared with the β-D-Gal-O-Me used as reference. To deepen our understanding of the binding mode of the best glycomimetics involved in the recognition process, molecular modeling studies, docking calculations, and NMR diffusion measurements have been performed. Although favorable complementary interactions induced by the addition of the hydrophobic aglycon might explain the affinity enhancement, experimental determination of the size and the topology of the multivalent conjugates further supported the formation of aggregative complexes as a major multivalent binding mode. This work represents a systematic and comprehensive study towards a thorough understanding of the protein-carbohydrate interactions involved in Pseudomonas aeruginosa infection, and as such should prove useful for the development of stable and optimized anti-adhesive agents. Copyright
Chabre, Yoann M.,Giguere, Denis,Blanchard, Bertrand,Rodrigue, Jacques,Rocheleau, Sylvain,Neault, Mathieu,Rauthu, Subhash,Papadopoulos, Alex,Arnold, Alexandre A.,Imberty, Anne,Roy, Rene
supporting information; experimental part
p. 6545 - 6562
(2011/08/07)

Synthesis of glycal-based chiral benzimidazoles by VO(acac) 2-CeCl3 combo catalyst and their self-aggregated nanostructured materials
(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.
supporting information; experimental part
p. 8086 - 8097
(2010/02/28)

α-glycosphingolipids via chelation-induced anomerization of O- And s-glucuronic and galacturonic acid derivatives
Bacterial glycolipids containing either α-glucuronic acid or α-galacturonic acid residues have an important role in the innate-type immune response to Gram-negative bacteria. Synthesis of closely related compounds, including a novel α-SO2 glycolipid mimetic, is described from carbohydrate precursors where anomerization is a key step. Very high stereoselectivites (>97:3 in favor of α) were observed from O-glycoside precursors.
Pilgrim, Wayne,Murphy, Paul V.
supporting information; experimental part
p. 939 - 942
(2009/09/08)

Regio- and stereo-selective synthesis of aryl 2-deoxy-C-glycopyranosides by palladium-catalyzed Heck coupling reactions of glycals and aryl iodides
The Heck coupling of aryl iodides with pyranoid glycals using a catalytic amount of Pd(OAc)2 to form pyranoid aryl C-glycosides has been achieved. The reaction takes place smoothly in the presence of Ag 2CO3 and Cu(OAc)2 (or DMSO) in acetonitrile. This arylation process, which occurs in a highly regio- and stereo-selective manner, provides a simple, mild, and efficient approach to the synthesis of aryl 2-deoxy-C-glycopyranosides.
Li, Hou-Hua,Ye, Xin-Shan
experimental part
p. 3855 - 3861
(2009/10/23)

Efficient synthesis of rare sugar D-allal via reversal of diastereoselection in the reduction of protected 1,5-anhydrohex-1-en-3-uloses: Protecting group dependence of the stereoselection
(Chemical Equation Presented) D-Allal was selectively obtained by reducing bulky-silyl-protected 1,5-anhydrohex-1-en-3-uloses using the NaBH4 - CeCl3·7H2O system. The crucial point of this synthesis is the nature of the pr
Fujiwara, Takashi,Hayashi, Masahiko
scheme or table
p. 9161 - 9163
(2009/04/04)

Generation of nitrile oxides under nanometer micelles built in neutral aqueous media: Synthesis of novel glycal-based chiral synthons and optically pure 2,8-dioxabicyclo[4.4.0]decene core
(Chemical Equation Presented) A highly efficient strategy for chemoselective oxidation of aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media is reported. Their in situ intermolecular 1,3-dipolar cycloaddition (1,3-DC) with olefins in nanometer aqueous micelles occurs with improved stereoselectivity and acceleration of reaction rate toward synthesis of new chiral synthons, 3-(2′-C-3′,4′,6′-tri-O- benzylglycal)-Δ2-isoxazolines and others. Construction of optically pure 2,8-dioxabicyclo[4.4.0]decene skeleta is performed by this green approach, and the stereochemistry of the new chiral center is predicted by B3LYP density functional theory.
Chatterjee, Nirbhik,Pandit, Palash,Halder, Samiran,Patra, Amarendra,Maiti, Dilip K.
p. 7775 - 7778
(2008/12/22)

RCM-based synthesis of a variety of β-C-glycosides and their in vitro anti-solid tumor activity
(Chemical Equation Presented) The synthesis of a number of biologically relevant C-glycosides has been carried out through the use of an esterification-ring-closing metathesis (RCM) strategy. The required acid precursors were readily prepared via a number of standard chemical transformations followed by dehydrative coupling of these acids with several olefin alcohols 1 to yield the precursor esters 3 in excellent yield. Methylenation of the esters 3 was followed by RCM and in situ hydroboration-oxidation of the formed glycals to furnish the protected β-C-glycosides 6 in good overall yield. Several examples were converted to the corresponding C-glycoglycerolipids 17 and subsequently screened against solid-tumor cell lines for in vitro differential cytotoxicity.
Postema, Maarten H. D.,Piper, Jared L.,Betts, Russell L.,Valeriote, Frederick A.,Pietraszkewicz, Halina
p. 829 - 836
(2007/10/03)

Aryl and arylmethyl C-glycosides through desulfitative stille and carbonylative stille cross-coupling of tinglycals and sulfonyl chlorides
The palladium-catalyzed cross-coupling of tinglucal and tingalactal derivatives with arenesulfonyl chlorides provides aryl C-glycoside precursors. Desulfitative carbonylative Stille cross-coupling between 1-naphthalenesulfonyl chloride and a tinglucal derivative gives, after stereoselective reduction of the keto moiety and stereoselective oxidative hydroboration, a protected form of 1-[(1S)-2,6-anhydro-L-glycero-D-gulo-heptitol-1-C-yl]naphthalene [β-C-glucopyranoside of (S)-(naphtha-1-yl)methanol]. Benzyl C-glycoside precursors are obtained by desulfitative Stille coupling of phenylmethanesulfonyl chloride with the corresponding protected tinglycals.
Dubbaka, Srinivas Reddy,Steunenberg, Peter,Vogel, Pierre
p. 1235 - 1238
(2007/10/03)

Synthesis of the JKLM-ring fragment of ciguatoxin
A stereoselective synthesis of the LM-ring fragment has been achieved starting from a sugar derivative. A stereoselective synthesis of the JKLM-ring fragment has been achieved through a coupling between two segments via heteroconjugate addition, seven-membered ether ring formation mediated by an acetylene cobalt complex, and spiroketalization reaction.
Baba, Takayuki,Huang, Guobin,Isobe, Minoru
p. 6851 - 6872
(2007/10/03)

Direct carbohydrate to carbocycle conversions via intramolecular allylation with Et2Zn/Pd(0)
Treatment of 5-vinylpyranosides with Et2Zn and catalytic Pd(0), in the presence of ZnCl2, results in the formation of 5-membered carbocyclic products. This carbohydrate ring-contraction features an intramolecular allylation of a ring-opened carbohydrate aldehyde by an in situ-generated nucleophilic allylzinc species. The stereoselectivity about vinyl and free hydroxyl groups at the newly created stereogenic centers varies from low to moderate while both its extent and sense are found to depend on particular structural features (e.g. the configuration of the starting carbohydrate).
Aurrecoechea, José M.,Arrate, Mónica,Gil, Jesús H.,López, Beatriz
p. 5515 - 5522
(2007/10/03)

Substituent effects on the SmI2/Pd(0)-promoted carbohydrate ring-contraction of 5-alkynylpyranosides
The effect of substituents on the reactivity and stereoselectivity of the SmI2/Pd(0)-promoted ring-contraction of 5-alkynylpyranosides has been examined using substrates substituted only at selected positions. While formation of 2-ethynylcyclopentanols takes place efficiently, an internal alkyne did not afford the expected product. The presence of peripheral alkoxy substituents leads to variable stereoselectivities that depend on the number and orientation of such groups. Thus, an isolated OBn substituent at C(3) (carbohydrate numbering) exerts a significant stereochemical control while additional substitution with the same group at C(4) either enhances or drastically reduces stereoselectivity depending on its orientation (α or β, respectively).
Aurrecoechea, José M.,Gil, Jesús H.,López, Beatriz
p. 7111 - 7121
(2007/10/03)

Immunomodulating glycosphingolipids: An efficient synthesis of a 2′-deoxy-α-galactosyl-GSL
A new and efficient approach to the total synthesis of 2′-deoxy-α-galactosyl glycosphingolipids was accomplished. Commercially available 3,4,6-tri-O-acetylgalactal was used as the chiral starting material for both the sugar and phytosphingosine building blocks required for the synthesis of 1-O-(2-deoxy-α-D-galactopyranosyl)-2-docosanoylamino-1,3, 4-octadecanetriol. The key step of the synthetic strategy was the stereoselective α-glycosidation of the azido precursor of sphingosine.
Costantino, Valeria,Fattorusso, Ernesto,Imperatore, Concetta,Mangoni, Alfonso
p. 369 - 375
(2007/10/03)

Syntheses of α- and β-glycosyl donors with a disaccharide β-D-Gal-(1→3)-D-GalNAc backbone
The synthesis of thioglycoside glycosyl donors with a disaccharide β-D-Gal-(1 → 3)-D-GalNAc backbone was studied using the glycosylation of a series of suitably protected 3-monohydroxy- and 3,4-dihydroxyderivatives of phenyl 2-azido-2-deoxy-1-thio-α- and 1-thio-β -D-galactopyranosides by galactosyl bromide, fluoride, and trichloroacetimidate. In the reaction with the monohydroxylated glycosyl acceptor, the process of intermolecular transfer of thiophenyl group from the glycosyl acceptor onto the cation formed from the molecule of glycosyl donor dominated. When glycosylating 3,4-diol under the same conditions, the product of the thiophenyl group transfer dominated or the undesired (1 → 4), rather than (1 → 3)-linked, disaccharide product formed. The aglycon transfer was excluded when 4-nitrophenylthio group was substituted for phenylthio group in the galactosyl acceptor molecule. This led to the target disaccharide, 4-nitrophenyl 2-azido-4,6-O-benzylidene-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β -D-galactopyranosyl)-1-thio-β-D-galactopyranoside, in 57% yield. This disaccharide product bears nonparticipating azido group in position 2 of galactosamine and can hence be used to form α-glycoside bond. Azido group and the aglycon nitro group were simultaneously reduced in this product and then trichloroacetylated, which led to the β-glycosyl donor, 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl) -1-thio-2-trichloroace-tamido-β-D-galactopyranoside, in 62% yield. The resulting glycosyl donor was used in the synthesis of tetrasaccharide asialo-GM1.
Cheshev,Kononov,Tsvetkov,Shashkov,Nifantiev
p. 419 - 429
(2007/10/03)

Organotransition metal modified sugars: Part 22. Direct metalation of glycals: Short and efficient routes to diversely protected stannylated glycals
A complete set of D-hexose-derived silyl and isopropylidene/silyl-protected glycals bearing complementary configurations at C-3 and C-4 has been synthesized in short and efficient 1-3 step sequences from standard precursors. The glycals have been applied to metalation reactions to give storable vinyl lithium equivalents by subsequent transmetalation to vinyl stannanes which represent valuable intermediates for transition metal-catalyzed cross-coupling reactions. A 1H-NMR-assisted conformational analysis has been carried out with the protected glycals and the stannylated congeners. The isopropylidene/silyl-protected glycals adopt the 4H5-conformation caused by the bicyclic system, whereas the conformations of the fully silyl-protected monocyclic glycals are mainly controlled by the vinylogous anomeric effect. The discussed galactal- and allal-derivatives show dynamic behaviour on the NMR-time-scale. At low temperatures the two possible conformers (4H5 and 5H4) have been observed demonstrating competition of steric congestion and stereoelectronic interaction via the vinylogous anomeric effect (VAE).
J?kel, Christoph,D?tz, Karl Heinz
p. 172 - 185
(2007/10/03)

Glycosylation using 2-azido-3,4,6-tri-O-benzyl-2-deoxy-D-glucose, - galactose, and -mannose with the aid of p-nitrobenzenesulfonyl chloride- silver trifluoromethanesulfonate-triethylamine system
This report describes a simple synthesis of 2-azido-3,4,6-tri-O-benzyl- 2-deoxy-D-glucopyranose. Glycosylation using this as well as 2-azido-3,4,6- tri-O-benzyl-2-deoxy-D-galactopyranose and -mannopyranose was achieved with the aid of a reagent system consisting of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine, and its modifications. O-(2-Acetamido-2-deoxy-β-D-glucopyranosyl)-(1 → 4)-O-α-D-mannopyranosyl- (1 → 4)-a-D-mannopyranose, the repeating unit of the main chain of the O- specific cell wall polysaccharide of E. coli 058 was synthesized.
Koto, Shinkiti,Asami, Kazuyasu,Hirooka, Motoko,Nagura, Kazuo,Takizawa, Mizue,Yamamoto, Satoko,Okamoto, Nami,Sato, Mitsuko,Tajima, Hiromi,Yoshida, Toyosaku,Nonaka, Nobuo,Sato, Tadaaki,Zen, Shonosuke,Yago, Kazuo,Tomonaga, Fumiya
p. 765 - 777
(2007/10/03)

Synthesis of Asialo GM1. New insights in the application of sulfonamidoglycosylation in oligosaccharide assembly: Subtle proximity effects in the stereochemical governance of glycosidation
The total synthesis of asialo GM1 (1a) has been accomplished. Using related chemistry, the methyl glycoside of the asialo compound (1b) has also been synthesized. These kinds of compounds have been identified as potential ligands for bacterial and viral infection sites. A simpler structure, which has also been identified for its infection attracting structure in the context of glycopeptides and glycolipids (methyl glycoside 2), has also been synthesized. The key common phase in the syntheses involves the sulfonamidoglycosidation reaction which is used to create a β-linkage leading to a ga1NAc residue joined to the C4 hydroxyl group of a galactose unit either as a monosaccharide (see compound 2) or as C4' in the context of a lactosyl moiety. During the course of these studies there was encountered an unusual 'proximal hydroxyl' directing effect. Thus, when C4 on the galactose ring of an azaglycosylating donor bears a free hydroxyl (see, for instance, compound 13), β-glycoside formation predominates. When this hydroxyl group is blocked, the process tends in the direction of α-glycoside formation (see compound 32). These findings were explained as arising from a critical intramolecular hydrogen bond between the C4 axial hydroxyl of the galactose donor and its proximal pyranosidal ring oxygen. This interaction stabilizes conformations from which β-glycosidation predominates.
Kwon, Ohyun,Danishefsky, Samuel J.
p. 1588 - 1599
(2007/10/03)

Selenoglycosides. 3. Synthesis of Phenyl 2-(N-Acetylamino)- and 2-Azido-2-deoxy-1-seleno-α-D-glycopyranosides via Azido-phenylselenylation of Diversely Protected Glycals
Two methods are described for the preparation of diversely protected phenyl 2-azido-2-deoxy-α-D-selenoglycopyranosides from protected glycals.In the first one (method A), a peracetylated glycal is treated with sodium azide and diphenyl diselenide in the presence of (diacetoxyiodo)benzene in dichloromethane at rt.With 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol (tri-O-acetyl-D-glucal) an inseparable mixture of phenyl 2-azido-2-deoxy-α-gluco- and -α-manno-selenoglycosides is obtained (91percent yield).With 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-lyxo-hex-1-enitol (tri-O-acetyl-D-galactal) only the α-galacto isomer is obtained (92percent).Method A is not compatible with benzyl groups.In method B, a perbenzylated glycal is reacted with trimethylsilyl azide and tetra-n-butylammonium fluoride in the presence of N-phenylselenophthalimide.From protected D-glucal a gluco/manno mixture is obtained, whereas only the galacto isomer is formed from protected D-galactal (75percent yield).The compatibility of method B with a variety of protecting groups is exemplified with 6-O-acetyl, 6-O-benzyl, and 6-O-(tert-butyldimethylsilyl)-3,4-O-isopropylidene-1,5-anhydro-2-deoxy-D-lyxo-hex-1-enitol.The same diastereocontrol is observed, and the α-D-galacto isomer is obtained (60-70percent yield).Reduction of the azido group of these selenoglycosides with 1,3-propanedithiol in the presence of triethylamine and acetylation affords the corresponding phenyl 2-(N-acetylamino)-2-deoxy-α-D-selenoglycopyranosides in good yield.
Czernecki, S.,Ayadi, E.,Randriamandimby, D.
p. 8256 - 8260
(2007/10/02)

A synthetic approach to the cis-fused marine pyranopyrans, (3E)- and (3Z)-dactomelyne. X-ray structure of a rare organomercurial
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Kozilowski,Lee
p. 863 - 870
(2007/10/02)

Syntheses of the methyl glycosides of the repeating units of chondroitin 4- and 6-sulfate.
3,4,6-Tri-O-acetyl-D-galactal was transformed into methyl 6-O-acetyl-2-azido-4-O-benzyl-2-deoxy-beta-D-galactopyranoside and its 4-O-acetyl-6-O-benzyl analogue, each of which was glycosylated with activated, O-acetylated derivatives of methyl D-glucopyranosyluronate. The resulting beta-(1----3)-linked disaccharide derivatives were each reductively N-acetylated, hydrogenolysed, O-sulfated, and saponified to afford the disodium salts of methyl 2-acetamido-2-deoxy-3-O-(beta-D-glucopyranosyluronic acid)-4-O-sulfo-beta-D-galactopyranoside and the 6-O-sulfo analogue. D-Galactal was also transformed into activated derivatives of 2-azido-3,6-di-O-benzyl-2-deoxy-D-galactopyranose and their 3,4-di-O-benzyl analogues with various substituents at O-4 and O-6. These glycosyl donors were condensed with 6-O-protected derivatives of methyl 2,3-di-O-benzyl-beta-D-glucopyranoside to give the beta-(1----4)-linked disaccharide derivatives, which were selectively deprotected, then oxidised at C-6 of the gluco unit, reductively N-acetylated, selectively deprotected, O-sulfated at C-4 or C-6 of the galacto unit, and hydrogenolysed to give the disodium salts of methyl 4-O-(2-acetamido-2-deoxy-4-O-sulfo-beta-D-galactopyranosyl)-beta-D- glucopyranosiduronic acid and the 6-O-sulfo analogue.
Jacquinet
p. 153 - 181
(2007/10/02)

Stereospecific Vorbrueggen-like Reactions of 1,2-Anhydro Sugars. An Alternative Route to the Synthesis of Nucleosides
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Chow, Ken,Danishefsky, Samuel
p. 4211 - 4214
(2007/10/02)

Einfache Synthese eines β(1-3)-verknuepften gal-galactal Disaccharids und dessen Verwendung in der N-Iodsuccinimid-aktivierten O-Glycopeptidsynthese
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Kessler, Horst,Kling, Andreas,Kottenhahn, Matthias
p. 452 - 454
(2007/10/02)

SYNTHESE DE PHOSPHORAMIDATES DE 2-DESOXY-2-IODOGLYCOSYLES
Addition of iodoazide to acetylated, benzylated, and methoxymethylated glycals yielded 2-deoxy-2-iodoglycosyl azides with 1,2-trans configuration.Stereoselectivity of the reaction favored the manno and talo configurations starting from D-glucal and D-galactal, respectively.With D-xylal derivatives, the stereoselectivity depended on the nature of the substituents.The Staudinger reaction of 2-deoxy-2-iodoglycosyl azides with trimethylphosphite led to the corresponding 2-deoxy-iodoglycosyl phosphoramidates in high yield.
Lafont, Dominique,Descotes, Gerard
p. 195 - 210
(2007/10/02)

Convenient Synthesis of Hex-1-enopyran-3-uloses: Selective Oxidation of Allylic Alcohols Using Pyridinium Dichromate
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Czernecki, S.,Vijayakumaran, K.,Ville, G.
p. 5472 - 5475
(2007/10/02)

ADDITION OF HALOGENOAZIDES TO GLYCALS
Addition of chloroazide to 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-lyxo- (1) and -D-arabino-hex-1-enitol (2) under u.v. irradiation proceeds regio- and stereo-selectively yielding mainly O-acetyl derivatives of 2-azido-2-deoxy-D-galactopyranose and -D-glucopyranose, respectively. 3,4,6-Tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosyl azide and 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-talopyranose (from 1), and 1,3,4,6-tetra-O-acetyl-2-chloro-2-deoxy-α-D-glucopyranosyl azide and 1,3,4,6-tetra-O-acetyl-2-azido-2-deoxy-α-D-mannopyranose (from 2) are byproducts. 1,5-Anhydro-3,4,6-tri-O-benzyl-2-deoxy-D-lyxo- and -D-arabino-hex-1-enitol reacted more rapidly with chloroazide, to give, under irradiation, derivatives of 2-azido-2-deoxy-D-galactose and -D-glucose, respectively.However, reaction in the dark gave mainly O-benzyl derivatives of 2-chloro-2-deoxy-α-D-galacto- and -α-D-glucopyranosyl azide.The difference between the products obtained may depend on the existence of two parallel processes, one radical (under irradiation), and the other ionic (reaction in the dark).
Bovin, Nicolai V.,Zurabyan, Sergei E.,Khorlin, Anatoly Y.
p. 25 - 36
(2007/10/02)