- Studies of Catalyst-Controlled Regioselective Acetalization and Its Application to Single-Pot Synthesis of Differentially Protected Saccharides
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This article describes studies on the regioselective acetal protection of monosaccharide-based diols using chiral phosphoric acids (CPAs) and their immobilized polymeric variants, (R)-Ad-TRIP-PS and (S)-SPINOL-PS, as the catalysts. These catalyst-controll
- Wang, Sibin,Zhelavskyi, Oleksii,Lee, Jeonghyo,Argüelles, Alonso J.,Khomutnyk, Yaroslav Ya.,Mensah, Enoch,Guo, Hao,Hourani, Rami,Zimmerman, Paul M.,Nagorny, Pavel
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supporting information
p. 18592 - 18604
(2021/11/16)
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- N -Glycosylation with sulfoxide donors for the synthesis of peptidonucleosides
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The synthesis of glycopyranosyl nucleosides modified in the sugar moiety has been less frequently explored, notably because of the lack of a reliable method to glycosylate pyrimidine bases. Herein we report a solution in the context of the synthesis of peptidonucleosides. They were obtained after glycosylation of different pyrimidine nucleobases with glucopyranosyl donors carrying an azide group at the C4 position. A methodological study involving different anomeric leaving groups (acetate, phenylsulfoxide and ortho-hexynylbenzoate) showed that a sulfoxide donor in combination with trimethylsilyl triflate as the promoter led to the best yields.
- Beau, Jean-Marie,Beretta, Margaux,Dr?ge, Thomas,Es-Sayed, Mazen,Nicolas, Lionel,Norsikian, Stéphanie,Rouchaud, Emilie,Vors, Jean-Pierre
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supporting information
p. 4285 - 4291
(2021/05/31)
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- Total Synthesis of the Echinodermatous Ganglioside LLG-3 Possessing the Biological Function of Promoting the Neurite Outgrowth
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A total synthesis of echinodermatous ganglioside LLG-3 with neuritogenic activity was accomplished by a convergent strategy. The synthesis of 2-hydroxyethyl 8-O-Me-α-sialoside 2 was started from the phenyl 7,8-di-O-Pico-thiosialoside 5, which can be chemoselectively removed the picoloyl group, and then the methyl group in 8-O-MeNeu5Ac moiety was chemoselectively prepared using TMSCHN2/FeCl3. For preparation of the terminal disialic unit, oxidative amidation was initially utilized by our group to efficiently construct the α(2,11) linkage of 8-O-Me-Neu5Acα(2,11)Neu5Gc. Herein, we also demonstrate that the synthesized ganglioside LLG-3 exhibited the neuritogenic activity toward the primary cortical neurons and that biological activity is superior to that of ganglioside DSG-A.
- Huang, Yuahn-Sieh,Shih, Jing-Feng,Tsai, Yow-Fu,Wu, Yu-Fa
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supporting information
p. 7491 - 7495
(2020/10/09)
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- Studies towards the total synthesis of repeating unit of O-sulfated polysaccharide from marine bacterium Cobetia pacifica KMM 3878
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Herein we report assembly of the appropriately protected trisaccharide repeating unit of Cobetia pacifica KMM 3878 O-sulfated polysaccharide. Our synthesis involves 3,4-O-pyruvilated galactose as the key building block which acts as a donor as well as acceptor in the construction of trisaccharide. We obtained the R isomer as a major stereoisomer in the pyruvilation reaction. The glycosylations proceeded with high stereo and regioselectivity.
- Pradhan, Kabita,Podilapu, Ananda Rao,Kulkarni, Suvarn S.
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p. 255 - 264
(2020/03/18)
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- Conformationally Switchable Glycosyl Donors
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Glycosyl donors functionalized with 2,2′-bipyridine moieties on the 3-OH and 6-OH or the 2-OH and 4-OH undergo a conformational change when forming 1:1 complexes with Zn2+ ions. The pyranoside ring of the zinc complexes adopted axial-rich skew boat conformations. The reactivities of the two glycosyl donors were investigated by performing a series of glycosylations in the presence or absence of Zn2+ ions. These glycosylations suggested a decrease in reactivity when binding Zn2+. The conformational effect of binding Zn2+ was therefore studied using a third glycosyl donor, unable to undergo conformational changes when binding Zn2+. From competition experiments, it was observed that the binding-induced conformational change increased the reactivity slightly compared to the glycosyl donor unable to undergo a conformational change.
- Holmstr?m, Thomas,Pedersen, Christian Marcus
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p. 13242 - 13251
(2019/11/03)
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- Synthesis of Glycosylated 1-Deoxynojirimycins Starting from Natural and Synthetic Disaccharides
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Iminosugars are an important class of natural products and have been subject to extensive studies in organic synthesis, bioorganic chemistry and medicinal chemistry, yet only a limited number of these studies are on glycosylated iminosugars. Here, a general route of synthesis is presented towards glycosylated 1-deoxynojirimycin derivatives based on the oxidation–reductive amination protocol that in the past has also been shown to be a versatile route towards 1-deoxynojirimycin. The strategy can be applied on commercial disaccharides, as shown in four examples, as well as on disaccharides that are not commercially available and are synthesized for this purpose, as shown by a fifth example.
- Liu, Bing,van Mechelen, Jeanine,van den Berg, Richard J. B. H. N.,van den Nieuwendijk, Adrianus M. C. H.,Aerts, Johannes M. F. G.,van der Marel, Gijsbert A.,Codée, Jeroen D. C.,Overkleeft, Herman S.
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p. 118 - 129
(2019/01/04)
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- Molecular-Level Understanding of the Major Fragmentation Mechanisms of Cellulose Fast Pyrolysis: An Experimental Approach Based on Isotopically Labeled Model Compounds
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Evaluation of the feasibility of various mechanisms possibly involved in cellulose fast pyrolysis is challenging. Therefore, selectively 13C-labeled cellotriose, 18O-labeled cellobiose, and 13C- and 18O-doubly-labeled cellobiose were synthesized and subjected to fast pyrolysis in an atmospheric pressure chemical ionization source of a linear quadrupole ion trap/orbitrap mass spectrometer. The initial products were immediately quenched, ionized using ammonium cations, and subsequently analyzed using the mass spectrometer. The loss or retention of isotope labels upon pyrolysis unambiguously revealed three major competing mechanisms - sequential losses of glycolaldehyde/ethenediol molecules from the reducing end (the reducing-end unraveling mechanism), hydroxymethylene-assisted glycosidic bond cleavage (HAGBC mechanism), and Maccoll elimination. Important discoveries include the following: (1) Reducing-end unraveling is the predominant mechanism occurring at the reducing end; (2) Maccoll elimination facilitates the cleaving of aglyconic bonds, and it is the mechanism leading to formation of reducing carbohydrates; 3) HAGBC occurs for glycosides but not at the reducing end of cellodextrins; 4) HAGBC and water loss are the predominant reactions for fast pyrolysis of 1,6-anhydrocellodextrins; and 5) HAGBC can proceed after reducing-end unraveling but unraveling does not occur once the HAGBC reaction pathway is initiated. Moreover, hydrolysis was conclusively ruled out for fast pyrolysis of cellobiose, cellotriose, and 1,6-anhydrocellodextrins up to cellotetraosan. No radical reactions were observed.
- Yu, Zaikuan J.,Easton, McKay W.,Murria, Priya,Xu, Lan,DIng, Duanchen,Jiang, Yuan,Zhang, Jifa,Kentt?maa, Hilkka I.
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p. 7037 - 7050
(2019/06/14)
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- Synthesis, biological evaluation and structure-activity relationship studies of hederacolchiside E and its derivatives as potential anti-Alzheimer agents
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Inspired by the previously reported neuroprotective activity of hederacolchiside E (1), we synthesized hederacolchiside E for the first time along with eleven of its derivatives. The neuroprotective effects of these compounds were further evaluated agains
- Li, Hui-ning,Liu, Yang,Zhang, Zuo-peng,Wang, Zhi-peng,Hao, Jing-zheng,Li, Feng-ran,Fan, Zhan-fang,Zou, Li-bo,Cheng, Mao-sheng
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p. 376 - 389
(2017/12/07)
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- Reengineering Chemical Glycosylation: Direct, Metal-Free Anomeric O-Arylation of Unactivated Carbohydrates
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To sustain innovation in glycobiology, effective routes to well-defined carbohydrate probes must be developed. For over a century, glycosylation has been dominated by the formation of the anomeric Csp3?O acetal junction in glycostructures. A dissociative mechanistic spectrum spanning SN1 and SN2 is frequently operational thereby reducing the efficiency. By reengineering this fundamental process, an orthogonal disconnection allows the acetal to be formed directly from the reducing sugar without the need for substrate pre-functionalisation. The use of stable aryliodonium salts facilitates a formal O?H functionalisation reaction. This allows lactols to undergo mild, metal-free O-arylation at ambient temperature. The efficiency of the transformation has been validated using a variety of pyranoside and furanoside monosaccharides in addition to biologically relevant di- and trisaccharides (up to 85 %). Fluorinated mechanistic probes that augment the anomeric effect were employed. It is envisaged that this strategy will prove expansive for the construction of complex acetals under substrate-based stereocontrol.
- Lucchetti, Nicola,Gilmour, Ryan
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supporting information
p. 16266 - 16270
(2018/10/24)
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- Conformational Distortion Using a Molecular Lever: Synthesis and Conformational Studies of Galactoside Derivatives
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Novel bicyclic d-galactose derivatives containing a molecular lever were synthesized and their conformations studied by 1H-NMR and crystallography. Increasing the bulkiness in the alkylidene ring in combination with introducing bulky O-protective groups on the pyranoside ring, causes a ring flip from a 4C1 into the axial rich 1C4 conformation. With less bulky protective groups, the pyranoside ring resides in the 4C1 conformation despite distortion of the external alkylidene ring.
- H?ner, Markus,Herrstedt Hammelev, Christian,Pedersen, Christian Marcus
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supporting information
p. 5532 - 5537
(2018/10/24)
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- Glycosyl Fluorides as Intermediates in BF3·OEt2-Promoted Glycosylation with Trichloroacetimidates
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Glycosyl fluorides have been found to be important intermediates in glycosylations with trichloroacetimidate donors and BF3·OEt2 activation (0.2–1 equiv.). Low-temperature NMR spectroscopy experiments revealed that the α-trichloroacetimidate was transformed into the glycosyl fluoride with inversion of stereochemistry, whereas the β anomer was not. A concerted mechanism was suggested for the stereospecific formation of glycosyl fluorides, which is not accounted for in the classic mechanism.
- Nielsen, Michael M.,Stougaard, Bolette A.,Bols, Mikael,Glibstrup, Emil,Pedersen, Christian M.
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supporting information
p. 1281 - 1284
(2017/03/17)
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- Synthesis of LewisX-O-Core-1 threonine: A building block for O-linked LewisX glycopeptides
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LewisX (LeX) is a branched trisaccharide Galβ1→4(Fucα1→3)GlcNAc that is expressed on many cell surface glycoproteins and plays critical roles in innate and adaptive immune responses. However, efficient synthesis of glycopeptides bearing LeX remains a major limitation for structure-function studies of the LeX determinant. Here we report a total synthesis of a LeX pentasaccharide 1 using a regioselective 1-benzenesulfinyl piperidine/triflic anhydride promoted [3 + 2] glycosylation. The presence of an Fmoc-threonine amino acid facilitates incorporation of the pentasaccharide in solid phase peptide synthesis, providing a route to diverse O-linked LeX glycopeptides. The described approach is broadly applicable to the synthesis of a variety of complex glycopeptides containing O-linked LeX or sialyl LewisX (sLeX).
- Sardar, Mohammed Y.R.,Krishnamurthy, Venkata R.,Park, Simon,Mandhapati, Appi Reddy,Wever, Walter J.,Park, Dayoung,Cummings, Richard D.,Chaikof, Elliot L.
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- Design, synthesis, and biological evaluation of crenatoside analogues as novel influenza neuraminidase inhibitors
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Natural products, especially derived from TCMH, have been found to exert antiviral effects against influenza virus. Crenatoside, a phenylethanoid glycoside from Pogostemon cablin Benth, which has been shown as a novel effective NA inhibitor previously, is considered as the leading compound for our further SARs studies. This work presented design, synthesis of novel crenatoside analogues from readily available d-Glucose and l-rhamnose in a convergent manner. Furthermore, their biological activities and SARs were also investigated. Especially, compound 2 h showed impressive IC50 = 27.77 μg/mL against NAs, which is 3 folds more potent than the leading compound crenatoside (IC50 = 89.81 μg/mL). These results would promise their therapeutic potential for influenza disease.
- Chen, Bao-Long,Wang, Ya-Jing,Guo, Hong,Zeng, Guang-Yao
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p. 199 - 205
(2016/01/16)
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- Efficient one-pot per-: O -acetylation-thioglycosidation of native sugars, 4,6- O -arylidenation and one-pot 4,6- O -benzylidenation-acetylation of S -/ O -glycosides catalyzed by Mg(OTf)2
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A sequential one-pot per-O-acetylation-S-/O-glycosidation of native mono and disaccharides under solvent free conditions using 0.5 mole% of Mg(OTf)2 as a non-hygroscopic, recyclable catalyst is reported. Regioselective 4,6-O-arylidenation of glycosides and thioglycosides with benzaldehyde or p-methoxybenzaldehyde dimethyl acetal is catalyzed by 10 mole% of Mg(OTf)2 to produce the corresponding 4,6-O-arylidenated product in high yields. Mg(OTf)2 can also mediate sequential one-pot benzylidenation-acetylation of mono and disaccharide based glycosides and thioglycosides in high yield.
- Mukherjee, Mana Mohan,Basu, Nabamita,Chaudhury, Aritra,Ghosh, Rina
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p. 109301 - 109314
(2016/11/30)
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- Borinic Acid Catalyzed Stereo- and Regioselective Couplings of Glycosyl Methanesulfonates
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In the presence of a diarylborinic acid catalyst, glycosyl methanesulfonates engage in regio- and stereoselective couplings with partially protected pyranoside and furanoside acceptors. The methanesulfonate donors are prepared in situ from glycosyl hemiacetals, and are coupled under mild, operationally simple conditions (amine base, organoboron catalyst, room temperature). The borinic acid catalyst not only influences site-selectivity via activation of 1,2- or 1,3-diol motifs, but also has a pronounced effect on the stereochemical outcome: 1,2-trans-linked disaccharides are obtained selectively in the absence of neighboring group participation. Reaction progress kinetic analysis was used to obtain insight into the mechanism of glycosylation, both in the presence of catalyst and in its absence, while rates of interconversion of methanesulfonate anomers were determined by NMR exchange spectroscopy (EXSY). Together, the results suggest that although the uncatalyzed and catalyzed reactions give rise to opposite stereochemical outcomes, both proceed by associative mechanisms.
- D'Angelo, Kyan A.,Taylor, Mark S.
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supporting information
p. 11058 - 11066
(2016/09/12)
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- Synthesis and Th1-immunostimulatory activity of α-galactosylceramide analogues bearing a halogen-containing or selenium-containing acyl chain
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A novel series of CD1d ligand α-galactosylceramides (α-GalCers) were synthesized by incorporation of the heavy atoms Br and Se in the acyl chain backbone of α-galactosyl-N-cerotoylphytosphingosine. The synthetic analogues are potent CD1d ligands and stimulate mouse invariant natural killer T (iNKT) cells to selectively enhance Th1 cytokine production. These synthetic analogues would be efficient X-ray crystallographic probes to disclose precise atomic positions of alkyl carbons and lipid–protein interactions in KRN7000/CD1d complexes.
- Hossain, Md. Imran,Hanashima, Shinya,Nomura, Takuto,Lethu, Sébastien,Tsuchikawa, Hiroshi,Murata, Michio,Kusaka, Hiroki,Kita, Shunsuke,Maenaka, Katsumi
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supporting information
p. 3687 - 3695
(2016/07/20)
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- Directing effect by remote electron-withdrawing protecting groups at O-3 or O-4 position of donors in glucosylations and galactosylations
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Glucosylations and galactosylations of various acceptors with donors possessing an electron-withdrawing benzylsulfonyl, benzoyl, or acetyl group at the O-3 or O-4 position were performed. A β-directing effect by the benzylsulfonyl group at O-3 of the glucosyl donors and by the benzylsulfonyl and acyl groups at O-4 of the glucosyl donors was observed. In contrast, acyl groups at O-3 of the glucosyl donors and acyl groups at O-3 and O-4 of the galactosyl donors exhibited an α-directing effect. The α-directing effect is partly considered to remote participation of the acyl groups, whereas the β-directing effect is somewhat attributed to the SN2-like reaction of the acceptor with the glycosyl triflate or the contact ion pair, which is stabilized by remote electron-withdrawing groups. Further evidence for the stability of the α-glycosyl triflates was determined by a low-temperature NMR study.
- Baek, Ju Yuel,Kwon, Hea-Won,Myung, Se Jin,Park, Jung Jun,Kim, Mi Young,Rathwell, Dominea C.K.,Jeon, Heung Bae,Seeberger, Peter H.,Kim, Kwan Soo
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supporting information
p. 5315 - 5320
(2015/07/15)
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- Total synthesis of LewisX using a late-stage crystalline intermediate
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Abstract Herein, we report on a highly efficient synthesis of a crystalline protected LewisX trisaccharide that was converted to LewisX following global deprotection. The trisaccharide was prepared in a highly convergent synthesis (seven steps, longest linear sequence) and in a 38% overall yield using a strategy that involved the regioselective glycosylation of a GlcNAc acceptor with a galactose thioglycoside donor, followed by fucosylation of the remaining free GlcNAc hydroxyl as key steps. The core trisaccharide also has the potential to be converted to other members of the Type-2 Lewis family of antigens due to the orthogonal nature of the protecting groups employed.
- Munneke, Stefan,Painter, Gavin F.,Gainsford, Graeme J.,Stocker, Bridget L.,Timmer, Mattie S.M.
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- A tin-free regioselective radical de-o-benzylation by an intramolecular hydrogen atom transfer on carbohydrate templates
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Radically selective: A remarkable 1,7-hydrogen atom transfer of a benzylic hydrogen atom to an O-silylmethylene radical initiates a regioselective de-O-benzylation of benzylated saccharides. The reaction terminates by an ionic mechanism and is general for hydroxy benzylated substrates having a variety of functional groups. Copyright
- Attouche, Angie,Urban, Dominique,Beau, Jean-Marie
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p. 9572 - 9575
(2013/09/23)
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- The synthesis of pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)- [α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside
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Pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)-[α-L- rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside, a monodesmosidic saponin isolated from Paris polyphylla Smith var. yunnanensis with promised antitumor activities, was firstly synthesized from glucoside thiol v
- Luo, Xin-Feng,Lei, Fan,He, Yi,Pei, Shu-Chen,Hai, Li,Qian, Shan,Wu, Yong
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experimental part
p. 314 - 321
(2012/09/07)
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- 2,4,6-Trichloro-1,3,5-triazine (TCT) mediated one-pot sequential functionalisation of glycosides for the generation of orthogonally protected monosaccharide building blocks
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Orthogonally protected monosaccharide building blocks have been prepared using TCT in a one-pot multicomponent transformation. The process involves successive steps of arylidene acetalation, esterification and regioselective reductive acetal cleavage. High regioselectivity, scope for using a broad range of substrates, functional group tolerance, mild reaction conditions, easy handling process and wide application range are a few advantages of the current process.
- Tatina, Madhubabu,Yousuf, Syed Khalid,Mukherjee, Debaraj
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supporting information; experimental part
p. 5357 - 5360
(2012/07/30)
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- Copper(I)-mediated 1,2-metallate rearrangements of 1-metallated glycals
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1,2-Metallate rearrangements involving reaction of 1-metallated glycals with organolithium reagents under copper(I) mediation give alkenylpolyol chains in 45-91% yield (19 examples). The reaction was applied to a formal synthesis of KRN7000 as well as a synthesis of a 5,6-ceramide derivative. Georg Thieme Verlag Stuttgart · New York.
- Jarowicki, Krzysztof,Kocieski, Philip,Komsta, Zofia,Wojtasiewicz, Anna
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supporting information; experimental part
p. 946 - 952
(2012/05/04)
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- Copper(II) triflate: A versatile catalyst for the one-pot preparation of orthogonally protected glycosides
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The development of general and expedient methodologies for the preparation of orthogonally protected glycoside building blocks is essential for the efficient synthesis of complex oligosaccharides. Herein, we describe a new approach that uses copper(II) triflate as a versatile catalyst for the one-pot preparation of orthogonal protected thio- and O-glycosides from the corresponding unprotected counterparts. The conditions are mild, easy to handle and applicable to two and three one-pot tandem transformations, which include arylidene acetalation, esterification, regioselective reductive acetal ring opening, glycosylation and silylation processes. Copyright
- Tran, Anh-Tuan,Jones, Rachel A.,Pastor, Julien,Boisson, Julien,Smith, Nichola,Galan, M. Carmen
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supporting information; experimental part
p. 2593 - 2598
(2011/12/04)
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- FeCl3 mediated arylidenation of carbohydrates
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Glycosides and thioglycosides based on monosaccharides in reaction with benzaldehyde dimethylacetal or p-methoxybenzaldehyde dimethyl acetal undergo FeCl3-catalyzed (20 mol %) regioselective 4,6-O-arylidenation producing the corresponding acetals in high yields. FeCl3 also mediates acetalation of glycosides and thioglycosides of cellobiose, maltose, and lactose affording the corresponding 4′,6′-O-benzylidene acetals, which were isolated after their acetylation in situ with acetic anhydride and pyridine. The combined yields (two steps) of these final products are also high (61-84%). The procedure is applicable to a wide variety of functional groups including -OBn.
- Basu, Nabamita,Maity, Sajal K.,Roy, Soumik,Singha, Shuvendu,Ghosh, Rina
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experimental part
p. 534 - 539
(2011/04/27)
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- Environmentally benign preparation of benzylidene acetal of carbohydrate derivatives in PEG 600
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An environmentally benign preparation of benzylidene acetal of carbohydrate derivatives catalyzed by HClO4-SiO2 in PEG 600 as solvent has been developed. Yields were excellent in every case. Copyright Taylor & Francis Group, LLC.
- Sau, Abhijit,Misra, Anup Kumar
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experimental part
p. 41 - 46
(2012/01/17)
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- Iodine-catalyzed one-pot acetalation-esterification reaction for the preparation of orthogonally protected glycosides
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An iodine-catalyzed one-pot tandem acetalation-esterification reaction of thio- and O-glycosides has been developed providing a fast and mild route to orthogonally protected glycosides ready to be used as building blocks in glycosylation reactions.
- Jones, Rachel A.,Davidson, Robert,Tran, Anh Tuan,Smith, Nichola,Carmen Galan
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experimental part
p. 1842 - 1845
(2010/10/18)
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- Synthesis and evaluation of 3″- and 4″-deoxy and -fluoro analogs of the immunostimulatory glycolipid, KRN7000
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Four 3″- and 4″-deoxy and -fluorogalactosyl ceramides were synthesized, and their ability to stimulate iNKT cells, based on levels of IL-2 production, was assessed in three NKT cell receptor hybridomas. In two of the hybridomas, 1.2 and 2H4, all of the analogs were immunostimulatory, while in the 1.4 hybridoma only the 4″-fluoro analog led to the production of significant levels of IL-2.
- Raju, Ravinder,Castillo, Bernard F.,Richardson, Stewart K.,Thakur, Meena,Severins, Ryan,Kronenberg, Mitchell,Howell, Amy R.
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supporting information; experimental part
p. 4122 - 4125
(2010/04/29)
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- Az-a colourful azulene-derived protecting group
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Azulen-1-yl-dicarbonyl (Az) is a novel, coloured, protecting group used to mask primary and secondary alcohols. In particular, the use of Az in the construction of carbohydrates, where a number of orthogonal protecting groups are typically required, is of
- Timmer, Mattie S.M.,Stocker, Bridget L.,Northcote, Peter T.,Burkett, Brendan A.
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supporting information; experimental part
p. 7199 - 7204
(2010/03/01)
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- The first total synthesis of telephiose A
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The first total synthesis of telephiose A (1), a novel trisaccharide ester having two acetyl groups and two benzoyl groups, was achieved by using glucosyl donor 6 and disaccharide acceptor 12. The crucial key step was the stereoselective construction of t
- Sato, Ken-ichi,Sakai, Koudai,Tsushima, Keiko,Akai, Shoji
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p. 3745 - 3748
(2008/02/09)
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- PROCESS FOR PRODUCING 1,2-TRANS-GLYCOSIDE COMPOUND
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In preparing a glycoside compound from (a) a furanose compound or pyranose compound, and (b) an alcohol compound, a process for preparing a glycoside compound in which glycosidic bond locates selectively trans form relative to C-2 hydroxyl group, the proc
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Page/Page column 9
(2010/11/28)
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- Synthesis of oligosaccharides corresponding to the polysaccharides of Lactobacillus and Thermophilus strains
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Synthesis of a branched trisaccharide and a tetrasaccharide repeating units corresponding to the polysaccharides of Lactobacillus spp. G-77 and Thermus thermophilus Samu-SA1 as their methyl glycosides has been achieved in excellent yield. Most of the glycosyl linkages are 1,2-cis in these oligosaccharide fragments. Georg Thieme Verlag Stuttgart.
- Mandal, Pintu Kumar,Misra, Anup Kumar
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p. 2660 - 2666
(2008/03/14)
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- A convergent ring-closing metathesis approach to carbohydrate-based macrolides with potential antibiotic activity
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An efficient convergent approach has been developed for the construction of novel, non-natural, carbohydrate-based macrolides. The key step in the synthesis is the formation of the macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been screened for biological activity against Gram-positive and Gram-negative bacteria, including resistant strains, yeasts, and molds.
- Blom, Petra,Ruttens, Bart,Van Hoof, Steven,Hubrecht, Idzi,Van Der Eycken, Johan,Sas, Benedikt,Van Hemel, Johan,Vandenkerckhove, Jan
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p. 10109 - 10112
(2007/10/03)
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- A facile synthesis of the GalNAcβ1→4Gal target sequence of respiratory pathogens
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The carbohydrate sequence, GalNAcβ1→4Gal, is the target for the adhesion of several respiratory pathogens. The sequence was prepared in an optimized synthesis in forms that allow conjugation to scaffolds or surfaces.
- Autar, Reshma,Liskamp, Rob M. J.,Pieters, Roland J.
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p. 2436 - 2442
(2007/10/03)
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- An Efficient and Regioselective Deprotection Method for Acetylated Glycosides
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A new regioselective 2-O-deacetylation methodology of acetylated glycosides using 85% hydrazine hydrate in THF is described. Using this method, acetylated 1-thio-glycoside could also be selectively deprotected to give 3-O-deprotected compound.
- Li, Jubiao,Wang, Yanguang
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p. 211 - 217
(2007/10/03)
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- A facile protocol for direct conversion of unprotected sugars into phenyl 4,6-O-benzylidene-per-O-acetylated-1,2-trans-thioglycosides
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A short and practical methodology for conversion of unprotected D-glucose, maltose, cellobiose and lactose into the corresponding phenyl 4,6-O-benzylidine-per-O-acetylated-1,2-trans-thioglycosides is described. The protocol is based on the execution of five reaction steps (bromoacetylation, thiophenolysis under phase transfer catalysis conditions, deacetylation, benzylidenation and acetylation) in one continuous procedure and provides a fast access to the title compounds as pure crystalline products without chromatographic purification.
- Larsen, Kim,Olsen, Carl Erik,Motawia, Mohammed Saddik
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p. 199 - 202
(2007/10/03)
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- Regioselective Lipase-catalysed acylation of 4,6-O-benzylidene-α- and - β-D-pyranoside derivatives displaying a range of anomeric substituents
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The application of Lipase enzymes to effect regioselective C-3-O- acylation of 4,6-O-benzylidene-β-D-gluco- and -galactopyranosides displaying a range of anomeric substituents, and C-2-O-acylation of phenyl 4,6-O- benzylidene-α-D-glucopyranoside and ethyl 4,6-O-benzylidene-1-thio-α-D- glucopyranoside is reported. In particular this method has allowed introduction of a variety of acyl protecting groups at the C-3 hydroxyl group of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside 11.
- Gridley, Jonathan J.,Hacking, Andrew J.,Osborn, Helen M. I.,Spackman, David G.
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p. 14925 - 14946
(2007/10/03)
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- A Novel Cleavage of Allyl Protection
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A novel, efficient, and mild cleavage of allyl protection is developed employing perfluoroalkylation and subsequent elimination.
- Yu, Biao,Li, Bing,Zhang, Jianbo,Hui, Yongzheng
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p. 4871 - 4874
(2007/10/03)
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- Chemical synthesis of (4,6-Pyr)-Gal β1→4GlcNacβ1→3Fucβ1→OMe: A pyruvated trisaccharide related to the cell aggregation of the sponge Microciona prolifera
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4,6-O-[(R)-1-carboxylethylidene] Galβ1→4GlcNAcβ1→3Fucβ1→OMe, a pyruvated trisaccharide unit involved in the aggregation factor of the marine sponge Microciona prolifera, was synthesized stereospecifically and unambiguously employing thioglycosides as glycosyl donors to construct glycosidic bonds.
- Deng, Shaojiang,Yu, Biao,Guo, Zhongwu,Hui, Yongzheng
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p. 439 - 452
(2007/10/03)
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- A high yielding chemical synthesis of sialyl Lewis x tetrasaccharide and Lewis x trisaccharide; examples of regio- and stereodifferentiated glycosylations
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Virtually complete regioselective galactosylation of the diol acceptor p-methoxyphenyl 6-O-benzyl-2-deoxy-2-tetrachlorophthalimido-β-D- glucopyranoside (8) with the donor phenyl 2,3,4-tri-O-acetyl-6-O-benzyl-1- thio-β-D-galactopyranoside (11) gave the lactosamine derivative 14, which was fucosylated with the donor 15 to give the Le(x) trisaccharide glycoside 2 after deprotection. Regioselective sialylation of the partially protected Le(x) trisaccharide triol 24 with the sialyl donor 25 gave, after deprotection, the SLe(x) tetrasaccharide glycoside 1. The overall yields of 2 and 1 from the monosaccharide starting materials 8, 11, 15, and 25 were 56% and 29%, respectively. In contrast to the virtually complete regio- and stereoselective galactosylation of 8, fucosylation with the benzyl-protected donor 15 gave the corresponding 1→3- and 1→4-linked disaccharides in a ratio of 3.6:1 (highly stereo- but not regioselective glycosylation), whereas fucosylation with acetyl-protected donor 18 gave a 2.2:1 β/α-mixture of 4- O-linked disaccharides (highly regio- but not stereoselective glycosylation).
- Ellervik, Ulf,Magnusson, Goeran
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p. 9314 - 9322
(2007/10/03)
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- Regioselective lipase-catalysed acylation of 4,6-O-benzylidene-β-D-pyranoside derivatives displaying a range of anomeric substituents
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The application of lipase enzymes to effect regioselective C-3-O-acylation of 4,6-O-benzylidene-β-D-gluco- and galactopyranosides displaying a range of anomeric substituents is reported. In particular this method has allowed introduction of a variety of acyl protecting groups at the C-3 hydroxyl group of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside 9.
- Gridley, Jonathan J.,Hacking, Andrew J.,Osborn, Helen M. I.,Spackman, David G.
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p. 1397 - 1399
(2007/10/03)
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- Chemical synthesis of 6'-α-maltosyl-maltotriose, a branched oligosaccharide representing the branch point of starch
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Chemical synthesis of the branched pentasaccharide 6'-α-maltosyl-maltotriose (15) is reported, based on the use of one synthon as a glycosyl acceptor and another synthon as a glycosyl donor. The synthon used as glycosyl acceptor was phenyl 2,3,6-tri-O-benzyl-1-thio-β-D-glucopyranoside (7) and was synthesized from D-glucose with phenyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside and phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside as key intermediates. The synthon used as glycosyl donor was O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-benzylα-D-glucopyranosyl)-(1 → 4)]-2,3-di-O-benzyl-α,β-D-glucopyranosyl trichloroacetimidate (12) and was synthesized from phenyl O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)(1 → 4)]-2,3-di-O-acetyl-1-thio-β-D-glucopyranoside with O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1 → 6)-O-[(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-(1 → 4)]-2,3-di-O-benzyl-D-glucopyranose as an intermediate. Condensation of compounds 7 and 12 followed by removal of the phenylthio group and debenzylation provided the branched pentasaccharide 15. Alternatively, the branched pentasaccharide was produced from amylopectin by consecutive alpha- and beta-amylase treatments and purified by chromatography. The identity of the products obtained by chemical synthesis and enzymatic hydrolysis is documented by 1H and 13C NMR spectra.
- Motawia,Olsen,Enevoldsen,Marcussen,Moller
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p. 109 - 123
(2007/10/02)
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- Practical synthesis of oligosaccharides. Partial synthesis of avermectin B(1a)
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A practical synthesis of oligosaccharides from phenylthio sugars via glycosyl fluorides is described. The new technology is applied to the synthesis of hexasaccharide 9 from a glucose derivative and avermectin B1a(11) from an avermectin B1
- Nicolaou,Dolle,Papahatjis,Randall,Dolle
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p. 4189 - 4192
(2007/10/02)
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- HYDROGENOLYSIS OF THE BENZYLIDENE ACETALS OF THIOGLYCOSIDES WITH THE LiAlH4-AlCl3 REAGENT. SYNTHESIS OF PARTIALLY BENZYLATED THIOGLYCOSIDE DERIVATIVES
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Reductive hydrogenolysis of phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-gluco- (4) and -galactopyranoside (8) and phenyl 2,3,6,2',3'-penta-O-benzyl-4',6'-O-benzylidene-1-thio-β-cellobioside (15) with the LiAlH4-AlCl3 reagent resulted in the corres
- Liptak, A.,Jodal, I.,Harangi, J.,Nanasi, P.
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p. 415 - 422
(2007/10/02)
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